Coated endovascular AAA device

ABSTRACT

Medical devices, and in particular implantable medical devices, may be coated to minimize or substantially eliminate a biological organism&#39;s reaction to the introduction of the medical device to the organism. The medical devices may be coated with any number of biocompatible materials. Therapeutic drugs, agents or compounds may be mixed with the biocompatible materials and affixed to at least a portion of the medical device. These therapeutic drugs, agents or compounds may also further reduce a biological organism&#39;s reaction to the introduction of the medical device to the organism. In addition, these therapeutic drugs, agents and/or compounds may be utilized to promote healing, including the formation of blood clots. Various materials and coating methodologies may be utilized to maintain the drugs, agents or compounds on the medical device until delivered and positioned.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to the local administration ofdrug/drug combinations for the prevention and treatment of vasculardisease, and more particularly to intraluminal medical devices for thelocal delivery of drug/drug combinations for the prevention andtreatment of vascular disease caused by injury and methods formaintaining the drug/drug combinations on the intraluminal medicaldevices. The present invention also relates to medical devices havingdrugs, agents and/or compounds affixed thereto to treat and preventdisease and minimize or substantially eliminate a biological organism'sreaction to the introduction of the medical device to the organism. Inaddition, the drugs, agents and/or compounds may be utilized to promotehealing.

[0003] 2. Discussion of the Related Art

[0004] Many individuals suffer from circulatory disease caused by aprogressive blockage of the blood vessels that profuse the heart andother major organs. More severe blockage of blood vessels in suchindividuals often leads to hypertension, ischemic injury, stroke, ormyocardial infarction. Atherosclerotic lesions, which limit or obstructcoronary blood flow, are the major cause of ischemic heart disease.Percutaneous transluminal coronary angioplasty is a medical procedurewhose purpose is to increase blood flow through an artery. Percutaneoustransluminal coronary angioplasty is the predominant treatment forcoronary vessel stenosis. The increasing use of this procedure isattributable to its relatively high success rate and its minimalinvasiveness compared with coronary bypass surgery. A limitationassociated with percutaneous transluminal coronary angioplasty is theabrupt closure of the vessel, which may occur immediately after theprocedure and restenosis, which occurs gradually following theprocedure. Additionally, restenosis is a chronic problem in patients whohave undergone saphenous vein bypass grafting. The mechanism of acuteocclusion appears to involve several factors and may result fromvascular recoil with resultant closure of the artery and/or depositionof blood platelets and fibrin along the damaged length of the newlyopened blood vessel.

[0005] Restenosis after percutaneous transluminal coronary angioplastyis a more gradual process initiated by vascular injury. Multipleprocesses, including thrombosis, inflammation, growth factor andcytokine release, cell proliferation, cell migration and extracellularmatrix synthesis each contribute to the restenotic process.

[0006] While the exact mechanism of restenosis is not completelyunderstood, the general aspects of the restenosis process have beenidentified. In the normal arterial wall, smooth muscle cells proliferateat a low rate, approximately less than 0.1 percent per day. Smoothmuscle cells in the vessel walls exist in a contractile phenotypecharacterized by eighty to ninety percent of the cell cytoplasmic volumeoccupied with the contractile apparatus. Endoplasmic reticulum, Golgi,and free ribosomes are few and are located in the perinuclear region.Extracellular matrix surrounds the smooth muscle cells and is rich inheparin-like glycosylaminoglycans, which are believed to be responsiblefor maintaining smooth muscle cells in the contractile phenotypic state(Campbell and Campbell, 1985).

[0007] Upon pressure expansion of an intracoronary balloon catheterduring angioplasty, smooth muscle cells within the vessel wall becomeinjured, initiating a thrombotic and inflammatory response. Cell derivedgrowth factors such as platelet derived growth factor, basic fibroblastgrowth factor, epidermal growth factor, thrombin, etc., released fromplatelets, invading macrophages and/or leukocytes, or directly from thesmooth muscle cells provoke a proliferative and migratory response inmedial smooth muscle cells. These cells undergo a change from thecontractile phenotype to a synthetic phenotype characterized by only afew contractile filament bundles, extensive rough endoplasmic reticulum,Golgi and free ribosomes. Proliferation/migration usually begins withinone to two days' post-injury and peaks several days thereafter (Campbelland Campbell, 1987; Clowes and Schwartz, 1985).

[0008] Daughter cells migrate to the intimal layer of arterial smoothmuscle and continue to proliferate and secrete significant amounts ofextracellular matrix proteins. Proliferation, migration andextracellular matrix synthesis continue until the damaged endotheliallayer is repaired at which time proliferation slows within the intima,usually within seven to fourteen days post-injury. The newly formedtissue is called neointima. The further vascular narrowing that occursover the next three to six months is due primarily to negative orconstrictive remodeling.

[0009] Simultaneous with local proliferation and migration, inflammatorycells adhere to the site of vascular injury. Within three to seven dayspost-injury, inflammatory cells have migrated to the deeper layers ofthe vessel wall. In animal models employing either balloon injury orstent implantation, inflammatory cells may persist at the site ofvascular injury for at least thirty days (Tanaka et al., 1993; Edelmanet al., 1998). Inflammatory cells therefore are present and maycontribute to both the acute and chronic phases of restenosis.

[0010] Numerous agents have been examined for presumedanti-proliferative actions in restenosis and have shown some activity inexperimental animal models. Some of the agents which have been shown tosuccessfully reduce the extent of intimal hyperplasia in animal modelsinclude: heparin and heparin fragments (Clowes, A. W. and Karnovsky M.,Nature 265: 25-26, 1977; Guyton, J. R. et al., Circ. Res., 46: 625-634,1980; Clowes, A. W. and Clowes, M. M., Lab. Invest. 52: 611-616, 1985;Clowes, A. W. and Clowes, M. M., Circ. Res. 58: 839-845, 1986; Majeskyet al., Circ. Res. 61: 296-300, 1987; Snow et al., Am. J. Pathol. 137:313-330, 1990; Okada, T. et al., Neurosurgery 25: 92-98, 1989),colchicine (Currier, J. W. et al., Circ. 80: 11-66, 1989), taxol(Sollot, S. J. et al., J. Clin. Invest. 95: 1869-1876, 1995),angiotensin converting enzyme (ACE) inhibitors (Powell, J. S. et al.,Science, 245: 186-188, 1989), angiopeptin (Lundergan, C. F. et al. Am.J. Cardiol. 17(Suppl. B):132B-136B, 1991), cyclosporin A (Jonasson, L.et al., Proc. Natl., Acad. Sci., 85: 2303, 1988), goat-anti-rabbit PDGFantibody (Ferns, G. A. A., et al., Science 253: 1129-1132, 1991),terbinafine (Nemecek, G. M. et al., J. Pharmacol. Exp. Thera. 248:1167-1174, 1989), trapidil (Liu, M. W. et al., Circ. 81: 1089-1093,1990), tranilast (Fukuyama, J. et al., Eur. J. Pharmacol. 318: 327-332,1996), interferon-gamma (Hansson, G. K. and Holm, J., Circ. 84:1266-1272, 1991), rapamycin (Marx, S. O. et al., Circ. Res. 76: 412-417,1995), steroids (Colburn, M. D. et al., J. Vasc. Surg. 15: 510-518,1992), see also Berk, B. C. et al., J. Am. Coll. Cardiol. 17: 111B-117B,1991), ionizing radiation (Weinberger, J. et al., Int. J. Rad. Onc.Biol. Phys. 36: 767-775, 1996), fusion toxins (Farb, A. et al., Circ.Res. 80: 542-550, 1997) antisense oligionucleotides (Simons, M. et al.,Nature 359: 67-70, 1992) and gene vectors (Chang, M. W. et al., J. Clin.Invest. 96: 2260-2268, 1995). Anti-proliferative action on smooth musclecells in vitro has been demonstrated for many of these agents, includingheparin and heparin conjugates, taxol, tranilast, colchicine, ACEinhibitors, fusion toxins, antisense oligionucleotides, rapamycin andionizing radiation. Thus, agents with diverse mechanisms of smoothmuscle cell inhibition may have therapeutic utility in reducing intimalhyperplasia.

[0011] However, in contrast to animal models, attempts in humanangioplasty patients to prevent restenosis by systemic pharmacologicmeans have thus far been unsuccessful. Neither aspirin-dipyridamole,ticlopidine, anti-coagulant therapy (acute heparin, chronic warfarin,hirudin or hirulog), thromboxane receptor antagonism nor steroids havebeen effective in preventing restenosis, although platelet inhibitorshave been effective in preventing acute reocclusion after angioplasty(Mak and Topol, 1997; Lang et al., 1991; Popma et al., 1991). Theplatelet GP II_(b)/III_(a) receptor, antagonist, Reopro® is still understudy but Reopro® has not shown definitive results for the reduction inrestenosis following angioplasty and stenting. Other agents, which havealso been unsuccessful in the prevention of restenosis, include thecalcium channel antagonists, prostacyclin mimetics, angiotensinconverting enzyme inhibitors, serotonin receptor antagonists, andanti-proliferative agents. These agents must be given systemically,however, and attainment of a therapeutically effective dose may not bepossible; anti-proliferative (or anti-restenosis) concentrations mayexceed the known toxic concentrations of these agents so that levelssufficient to produce smooth muscle inhibition may not be reached (Makand Topol, 1997; Lang et al., 1991; Popma et al., 1991).

[0012] Additional clinical trials in which the effectiveness forpreventing restenosis utilizing dietary fish oil supplements orcholesterol lowering agents has been examined showing either conflictingor negative results so that no pharmacological agents are as yetclinically available to prevent post-angioplasty restenosis (Mak andTopol, 1997; Franklin and Faxon, 1993: Serruys, P. W. et al., 1993).Recent observations suggest that the antilipid/antioxident agent,probucol, may be useful in preventing restenosis but this work requiresconfirmation (Tardif et al., 1997; Yokoi, et al., 1997). Probucol ispresently not approved for use in the United States and a thirty-daypretreatment period would preclude its use in emergency angioplasty.Additionally, the application of ionizing radiation has shownsignificant promise in reducing or preventing restenosis afterangioplasty in patients with stents (Teirstein et al., 1997). Currently,however, the most effective treatments for restenosis are repeatangioplasty, atherectomy or coronary artery bypass grafting, because notherapeutic agents currently have Food and Drug Administration approvalfor use for the prevention of post-angioplasty restenosis.

[0013] Unlike systemic pharmacologic therapy, stents have proven usefulin significantly reducing restenosis. Typically, stents areballoon-expandable slotted metal tubes (usually, but not limited to,stainless steel), which, when expanded within the lumen of anangioplastied coronary artery, provide structural support through rigidscaffolding to the arterial wall. This support is helpful in maintainingvessel lumen patency. In two randomized clinical trials, stentsincreased angiographic success after percutaneous transluminal coronaryangioplasty, by increasing minimal lumen diameter and reducing, but noteliminating, the incidence of restenosis at six months (Serruys et al.,1994; Fischman et al., 1994).

[0014] Additionally, the heparin coating of stents appears to have theadded benefit of producing a reduction in sub-acute thrombosis afterstent implantation (Serruys et al., 1996). Thus, sustained mechanicalexpansion of a stenosed coronary artery with a stent has been shown toprovide some measure of restenosis prevention, and the coating of stentswith heparin has demonstrated both the feasibility and the clinicalusefulness of delivering drugs locally, at the site of injured tissue.

[0015] As stated above, the use of heparin coated stents demonstratesthe feasibility and clinical usefulness of local drug delivery; however,the manner in which the particular drug or drug combination is affixedto the local delivery device will play a role in the efficacy of thistype of treatment. For example, the processes and materials utilized toaffix the drug/drug combinations to the local delivery device should notinterfere with the operations of the drug/drug combinations. Inaddition, the processes and materials utilized should be biocompatibleand maintain the drug/drug combinations on the local device throughdelivery and over a given period of time. For example, removal of thedrug/drug combination during delivery of the local delivery device maypotentially cause failure of the device.

[0016] Accordingly, there exists a need for drug/drug combinations andassociated local delivery devices for the prevention and treatment ofvascular injury causing intimal thickening which is either biologicallyinduced, for example, atherosclerosis, or mechanically induced, forexample, through percutaneous transluminal coronary angioplasty. Inaddition, there exists a need for maintaining the drug/drug combinationson the local delivery device through delivery and positioning as well asensuring that the drug/drug combination is released in therapeuticdosages over a given period of time.

[0017] A variety of stent coatings and compositions have been proposedfor the prevention and treatment of injury causing intimal thickening.The coatings may be capable themselves of reducing the stimulus thestent provides to the injured lumen wall, thus reducing the tendencytowards thrombosis or restenosis. Alternately, the coating may deliver apharmaceutical/therapeutic agent or drug to the lumen that reducessmooth muscle tissue proliferation or restenosis. The mechanism fordelivery of the agent is through diffusion of the agent through either abulk polymer or through pores that are created in the polymer structure,or by erosion of a biodegradable coating.

[0018] Both bioabsorbable and biostable compositions have been reportedas coatings for stents. They generally have been polymeric coatings thateither encapsulate a pharmaceutical/therapeutic agent or drug, e.g.rapamycin, taxol etc., or bind such an agent to the surface, e.g.heparin-coated stents. These coatings are applied to the stent in anumber of ways, including, though not limited to, dip, spray, or spincoating processes.

[0019] One class of biostable materials that has been reported ascoatings for stents is polyfluoro homopolymers. Polytetrafluoroethylene(PTFE) homopolymers have been used as implants for many years. Thesehomopolymers are not soluble in any solvent at reasonable temperaturesand therefore are difficult to coat onto small medical devices whilemaintaining important features of the devices (e.g. slots in stents).

[0020] Stents with coatings made from polyvinylidenefluoridehomopolymers and containing pharmaceutical/therapeutic agents or drugsfor release have been suggested. However, like most crystallinepolyfluoro homopolymers, they are difficult to apply as high qualityfilms onto surfaces without subjecting them to relatively hightemperatures that correspond to the melting temperature of the polymer.

[0021] It would be advantageous to develop coatings for implantablemedical devices that will reduce thrombosis, restenosis, or otheradverse reactions, that may include, but do not require, the use ofpharmaceutical or therapeutic agents or drugs to achieve such affects,and that possess physical and mechanical properties effective for use insuch devices even when such coated devices are subjected to relativelylow maximum temperatures. It would also be advantageous to developimplantable medical devices in combination with various drugs, agentsand/or compounds which treat disease and minimize or substantiallyeliminate a living organisms' reaction to the implantation of themedical device. In certain circumstances, it may be advantageous todevelop implantable medical devices in combination with various drugs,agents and/or compounds which promote wound healing.

SUMMARY OF THE INVENTION

[0022] The drug/drug combination therapies, drug/drug combinationcarriers and associated local delivery devices of the present inventionprovide a means for overcoming the difficulties associated with themethods and devices currently in use, as briefly described above. Inaddition, the methods for maintaining the drug/drug combinationtherapies, drug/drug combination carriers on the local delivery deviceensure that the drug/drug combination therapies reach the target site.

[0023] In accordance with one aspect, the present invention is directedto a system for bypassing an aneurysm. The system comprises at least oneprosthesis for establishing a fluid flow path through an aneurysmalsection of artery, an anchoring element operatively associated with theat least one prosthesis for securing and sealing the at least oneprosthesis upstream of the aneurysmal section of artery, a biocompatiblevehicle affixed to at least one of the anchoring element and the atleast one prosthesis, and at least one agent in therapeutic dosagesincorporated into the biocompatible material for the promotion of awound healing response.

[0024] In accordance with another aspect, the present invention isdirected to a system for bypassing an aneurysm. The system comprises atleast one prosthesis for establishing a fluid flow path through ananeurysmal section of artery, an anchoring element operativelyassociated with the at least one prosthesis for securing and sealing theat least one prosthesis upstream of the aneurysmal section of artery andat least one agent in therapeutic dosages affixed to at least one of theanchoring element and the at least one prosthesis for the promotion of awound healing response.

[0025] The medical devices, drug coatings and methods for maintainingthe drug coatings or vehicles thereon of the present invention utilizesa combination of materials to treat disease, and reactions by livingorganisms due to the implantation of medical devices for the treatmentof disease or other conditions. The local delivery of drugs, agents orcompounds generally substantially reduces the potential toxicity of thedrugs, agents or compounds when compared to systemic delivery whileincreasing their efficacy.

[0026] Drugs, agents or compounds may be affixed to any number ofmedical devices to treat various diseases. The drugs, agents orcompounds may also be affixed to minimize or substantially eliminate thebiological organism's reaction to the introduction of the medical deviceutilized to treat a separate condition. For example, stents may beintroduced to open coronary arteries or other body lumens such asbiliary ducts. The introduction of these stents cause a smooth musclecell proliferation effect as well as inflammation. Accordingly, thestents may be coated with drugs, agents or compounds to combat thesereactions. Anastomosis devices, routinely utilized in certain types ofsurgery, may also cause a smooth muscle cell proliferation effect aswell as inflammation. Stent-grafts and systems utilizing stent-grafts,for example, aneurysm bypass systems may be coated with drugs, agentsand/or compounds which prevent adverse affects caused by theintroduction of these devices as well as to promote healing andincorporation. Therefore, the devices may also be coated with drugs,agents and/or compounds to combat these reactions. In addition, devicessuch as aneurysm bypass systems may be coated with drugs, agents and/orcompounds that promote would healing, thereby reducing the risk ofendoleaks or other similar phenomena.

[0027] The drugs, agents or compounds will vary depending upon the typeof medical device, the reaction to the introduction of the medicaldevice and/or the disease sought to be treated. The type of coating orvehicle utilized to immobilize the drugs, agents or compounds to themedical device may also vary depending on a number of factors, includingthe type of medical device, the type of drug, agent or compound and therate of release thereof.

[0028] In order to be effective, the drugs, agents or compounds shouldpreferably remain on the medical devices during delivery andimplantation. Accordingly, various coating techniques for creatingstrong bonds between the drugs, agents or compounds may be utilized. Inaddition, various materials may be utilized as surface modifications toprevent the drugs, agents or compounds from coming off prematurely.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The foregoing and other features and advantages of the inventionwill be apparent from the following, more particular description ofpreferred embodiments of the invention, as illustrated in theaccompanying drawings.

[0030]FIG. 1 is a view along the length of a stent (ends not shown)prior to expansion showing the exterior surface of the stent and thecharacteristic banding pattern.

[0031]FIG. 2 is a perspective view along the length of the stent of FIG.1 having reservoirs in accordance with the present invention.

[0032]FIG. 3 indicates the fraction of drug released as a function oftime from coatings of the present invention over which no topcoat hasbeen disposed.

[0033]FIG. 4 indicates the fraction of drug released as a function oftime from coatings of the present invention including a topcoat disposedthereon.

[0034]FIG. 5 indicates the fraction of drug released as a function oftime from coatings of the present invention over which no topcoat hasbeen disposed.

[0035]FIG. 6 indicates in vivo stent release kinetics of rapamycin frompoly(VDF/HFP).

[0036]FIG. 7 is a cross-sectional view of a band of the stent of FIG. 1having drug coatings thereon in accordance with a first exemplaryembodiment of the invention.

[0037]FIG. 8 is a cross-sectional view of a band of the stent of FIG. 1having drug coatings thereon in accordance with a second exemplaryembodiment of the invention.

[0038]FIG. 9 is a cross-sectional view of a band of the stent of FIG. 1having drug coatings thereon in accordance with a third exemplaryembodiment of the present invention.

[0039] FIGS. 10-13 illustrate an exemplary one-piece embodiment of ananastomosis device having a fastening flange and attached staple membersin accordance with the present invention.

[0040]FIG. 14 is a side view of an apparatus for joining anatomicalstructures together, according to an exemplary embodiment of theinvention.

[0041]FIG. 15 is a cross-sectional view showing a needle portion of theFIG. 14 apparatus passing through edges of anatomical structures,according to an exemplary embodiment of the invention.

[0042]FIG. 16 is a cross-sectional view showing the FIG. 14 apparatuspulled through an anastomosis, according to an exemplary embodiment ofthe invention.

[0043]FIG. 17 is a cross-sectional view showing a staple of the FIG. 14apparatus being placed into proximity with the anatomical structures,according to an exemplary embodiment of the invention FIG. 18 is across-sectional view showing a staple of the FIG. 14 apparatus beingengaged on both sides of the anastomosis, according to an exemplaryembodiment of the invention.

[0044]FIG. 19 is a cross-sectional view showing a staple after it hasbeen crimped to join the anatomical structures, according to anexemplary embodiment of the invention.

[0045]FIG. 20 is a cross-sectional view of a balloon having a lubriciouscoating affixed thereto in accordance with the present invention.

[0046]FIG. 21 is a cross-sectional view of a band of the stent in FIG. 1having a lubricious coating affixed thereto in accordance with thepresent invention.

[0047]FIG. 22 is a partial cross-sectional view of a self-expandingstent in a delivery device having a lubricious coating in accordancewith the present invention.

[0048]FIG. 23 is a cross-sectional view of a band of the stent in FIG. 1having a modified polymer coating in accordance with the presentinvention.

[0049]FIG. 24 is a side elevation of an exemplary stent-graft inaccordance with the present invention.

[0050]FIG. 25 is a fragmentary cross-sectional view of another alternateexemplary embodiment of a stent-graft in accordance with the presentinvention.

[0051]FIG. 26 is a fragmentary cross-sectional view of another alternateexemplary embodiment of a stent-graft in accordance with the presentinvention.

[0052]FIG. 27 is an elevation view of a fully deployed aortic repairsystem in accordance with the present invention.

[0053]FIG. 28 is a perspective view of a stent for a first prosthesis,shown for clarity in an expanded state, in accordance with the presentinvention.

[0054]FIG. 29 is a perspective view of a first prosthesis having a stentcovered by a gasket material in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0055] The drug/drug combinations and delivery devices of the presentinvention may be utilized to effectively prevent and treat vasculardisease, and in particular, vascular disease caused by injury. Variousmedical treatment devices utilized in the treatment of vascular diseasemay ultimately induce further complications. For example, balloonangioplasty is a procedure utilized to increase blood flow through anartery and is the predominant treatment for coronary vessel stenosis.However, as stated above, the procedure typically causes a certaindegree of damage to the vessel wall, thereby potentially exacerbatingthe problem at a point later in time. Although other procedures anddiseases may cause similar injury, exemplary embodiments of the presentinvention will be described with respect to the treatment of restenosisand related complications following percutaneous transluminal coronaryangioplasty and other similar arterial/venous procedures, including thejoining of arteries, veins and other fluid carrying conduits.

[0056] While exemplary embodiments of the invention will be describedwith respect to the treatment of restenosis and related complicationsfollowing percutaneous transluminal coronary angioplasty, it isimportant to note that the local delivery of drug/drug combinations maybe utilized to treat a wide variety of conditions utilizing any numberof medical devices, or to enhance the function and/or life of thedevice. For example, intraocular lenses, placed to restore vision aftercataract surgery is often compromised by the formation of a secondarycataract. The latter is often a result of cellular overgrowth on thelens surface and can be potentially minimized by combining a drug ordrugs with the device. Other medical devices which often fail due totissue in-growth or accumulation of proteinaceous material in, on andaround the device, such as shunts for hydrocephalus, dialysis grafts,colostomy bag attachment devices, ear drainage tubes, leads for pacemakers and implantable defibrillators can also benefit from thedevice-drug combination approach. Devices which serve to improve thestructure and function of tissue or organ may also show benefits whencombined with the appropriate agent or agents. For example, improvedosteointegration of orthopedic devices to enhance stabilization of theimplanted device could potentially be achieved by combining it withagents such as bone-morphogenic protein. Similarly other surgicaldevices, sutures, staples, anastomosis devices, vertebral disks, bonepins, suture anchors, hemostatic barriers, clamps, screws, plates,clips, vascular implants, tissue adhesives and sealants, tissuescaffolds, various types of dressings, bone substitutes, intraluminaldevices, and vascular supports could also provide enhanced patientbenefit using this drug-device combination approach. Essentially, anytype of medical device may be coated in some fashion with a drug or drugcombination which enhances treatment over use of the singular use of thedevice or pharmaceutical agent.

[0057] In addition to various medical devices, the coatings on thesedevices may be used to deliver therapeutic and pharmaceutic agentsincluding: antiproliferative/antimitotic agents including naturalproducts such as vinca alkaloids (i.e. vinblastine, vincristine, andvinorelbine), paclitaxel, epidipodophyllotoxins (i.e. etoposide,teniposide), antibiotics (dactinomycin (actinomycin D) daunorubicin,doxorubicin and idarubicin), anthracyclines, mitoxantrone, bleomycins,plicamycin (mithramycin) and mitomycin, enzymes (L-asparaginase whichsystemically metabolizes L-asparagine and deprives cells which do nothave the capacity to synthesize their own asparagine); antiplateletagents such as G(GP) II_(b)/III_(a) inhibitors and vitronectin receptorantagonists; antiproliferative/antimitotic alkylating agents such asnitrogen mustards (mechlorethamine, cyclophosphamide and analogs,melphalan, chlorambucil), ethylenimines and methylmelamines(hexamethylmelamine and thiotepa), alkyl sulfonates-busulfan,nirtosoureas (carmustine (BCNU) and analogs, streptozocin),trazenes—dacarbazinine (DTIC); antiproliferative/antimitoticantimetabolites such as folic acid analogs (methotrexate), pyrimidineanalogs (fluorouracil, floxuridine, and cytarabine), purine analogs andrelated inhibitors (mercaptopurine, thioguanine, pentostatin and2-chlorodeoxyadenosine {cladribine}); platinum coordination complexes(cisplatin, carboplatin), procarbazine, hydroxyurea, mitotane,aminoglutethimide; hormones (i.e. estrogen); anticoagulants (heparin,synthetic heparin salts and other inhibitors of thrombin); fibrinolyticagents (such as tissue plasminogen activator, streptokinase andurokinase), aspirin, dipyridamole, ticlopidine, clopidogrel, abciximab;antimigratory; antisecretory (breveldin); anti-inflammatory: such asadrenocortical steroids (cortisol, cortisone, fludrocortisone,prednisone, prednisolone, 6α-methylprednisolone, triamcinolone,betamethasone, and dexamethasone), non-steroidal agents (salicylic acidderivatives i.e. aspirin; para-aminophenol derivatives i.e.acetominophen; indole and indene acetic acids (indomethacin, sulindac,and etodalac), heteroaryl acetic acids (tolmetin, diclofenac, andketorolac), arylpropionic acids (ibuprofen and derivatives), anthranilicacids (mefenamic acid, and meclofenamic acid), enolic acids (piroxicam,tenoxicam, phenylbutazone, and oxyphenthatrazone), nabumetone, goldcompounds (auranofin, aurothioglucose, gold sodium thiomalate);immunosuppressives: (cyclosporine, tacrolimus (FK-506), sirolimus(rapamycin), azathioprine, mycophenolate mofetil); angiogenic agents:vascular endothelial growth factor (VEGF), fibroblast growth factor(FGF); angiotensin receptor blockers; nitric oxide donors; anti-senseoligionucleotides and combinations thereof; cell cycle inhibitors, mTORinhibitors, and growth factor receptor signal transduction kinaseinhibitors; retenoids; cyclin/CDK inhibitors; HMG co-enzyme reductaseinhibitors (statins); and protease inhibitors.

[0058] As stated previously, the implantation of a coronary stent inconjunction with balloon angioplasty is highly effective in treatingacute vessel closure and may reduce the risk of restenosis.Intravascular ultrasound studies (Mintz et al., 1996) suggest thatcoronary stenting effectively prevents vessel constriction and that mostof the late luminal loss after stent implantation is due to plaquegrowth, probably related to neointimal hyperplasia. The late luminalloss after coronary stenting is almost two times higher than thatobserved after conventional balloon angioplasty. Thus, inasmuch asstents prevent at least a portion of the restenosis process, acombination of drugs, agents or compounds which prevents smooth musclecell proliferation, reduces inflammation and reduces coagulation orprevents smooth muscle cell proliferation by multiple mechanisms,reduces inflammation and reduces coagulation combined with a stent mayprovide the most efficacious treatment for post-angioplasty restenosis.The systemic use of drugs, agents or compounds in combination with thelocal delivery of the same or different drug/drug combinations may alsoprovide a beneficial treatment option.

[0059] The local delivery of drug/drug combinations from a stent has thefollowing advantages; namely, the prevention of vessel recoil andremodeling through the scaffolding action of the stent and theprevention of multiple components of neointimal hyperplasia orrestenosis as well as a reduction in inflammation and thrombosis. Thislocal administration of drugs, agents or compounds to stented coronaryarteries may also have additional therapeutic benefit. For example,higher tissue concentrations of the drugs, agents or compounds may beachieved utilizing local delivery, rather than systemic administration.In addition, reduced systemic toxicity may be achieved utilizing localdelivery rather than systemic administration while maintaining highertissue concentrations. Also in utilizing local delivery from a stentrather than systemic administration, a single procedure may suffice withbetter patient compliance. An additional benefit of combination drug,agent, and/or compound therapy may be to reduce the dose of each of thetherapeutic drugs, agents or compounds, thereby limiting their toxicity,while still achieving a reduction in restenosis, inflammation andthrombosis. Local stent-based therapy is therefore a means of improvingthe therapeutic ratio (efficacy/toxicity) of anti-restenosis,anti-inflammatory, anti-thrombotic drugs, agents or compounds.

[0060] There are a multiplicity of different stents that may be utilizedfollowing percutaneous transluminal coronary angioplasty. Although anynumber of stents may be utilized in accordance with the presentinvention, for simplicity, a limited number of stents will be describedin exemplary embodiments of the present invention. The skilled artisanwill recognize that any number of stents may be utilized in connectionwith the present invention. In addition, as stated above, other medicaldevices may be utilized.

[0061] A stent is commonly used as a tubular structure left inside thelumen of a duct to relieve an obstruction. Commonly, stents are insertedinto the lumen in a non-expanded form and are then expandedautonomously, or with the aid of a second device in situ. A typicalmethod of expansion occurs through the use of a catheter-mountedangioplasty balloon which is inflated within the stenosed vessel or bodypassageway in order to shear and disrupt the obstructions associatedwith the wall components of the vessel and to obtain an enlarged lumen.

[0062]FIG. 1 illustrates an exemplary stent 100 which may be utilized inaccordance with an exemplary embodiment of the present invention. Theexpandable cylindrical stent 100 comprises a fenestrated structure forplacement in a blood vessel, duct or lumen to hold the vessel, duct orlumen open, more particularly for protecting a segment of artery fromrestenosis after angioplasty. The stent 100 may be expandedcircumferentially and maintained in an expanded configuration, that iscircumferentially or radially rigid. The stent 100 is axially flexibleand when flexed at a band, the stent 100 avoids any externallyprotruding component parts.

[0063] The stent 100 generally comprises first and second ends with anintermediate section therebetween. The stent 100 has a longitudinal axisand comprises a plurality of longitudinally disposed bands 102, whereineach band 102 defines a generally continuous wave along a line segmentparallel to the longitudinal axis. A plurality of circumferentiallyarranged links 104 maintain the bands 102 in a substantially tubularstructure. Essentially, each longitudinally disposed band 102 isconnected at a plurality of periodic locations, by a shortcircumferentially arranged link 104 to an adjacent band 102. The waveassociated with each of the bands 102 has approximately the samefundamental spatial frequency in the intermediate section, and the bands102 are so disposed that the wave associated with them are generallyaligned so as to be generally in phase with one another. As illustratedin the figure, each longitudinally arranged band 102 undulates throughapproximately two cycles before there is a link to an adjacent band 102.

[0064] The stent 100 may be fabricated utilizing any number of methods.For example, the stent 100 may be fabricated from a hollow or formedstainless steel tube that may be machined using lasers, electricdischarge milling, chemical etching or other means. The stent 100 isinserted into the body and placed at the desired site in an unexpandedform. In one exemplary embodiment, expansion may be effected in a bloodvessel by a balloon catheter, where the final diameter of the stent 100is a function of the diameter of the balloon catheter used.

[0065] It should be appreciated that a stent 100 in accordance with thepresent invention may be embodied in a shape-memory material, including,for example, an appropriate alloy of nickel and titanium or stainlesssteel. Structures formed from stainless steel may be made self-expandingby configuring the stainless steel in a predetermined manner, forexample, by twisting it into a braided configuration. In this embodimentafter the stent 100 has been formed it may be compressed so as to occupya space sufficiently small as to permit its insertion in a blood vesselor other tissue by insertion means, wherein the insertion means includea suitable catheter, or flexible rod. On emerging from the catheter, thestent 100 may be configured to expand into the desired configurationwhere the expansion is automatic or triggered by a change in pressure,temperature or electrical stimulation.

[0066]FIG. 2 illustrates an exemplary embodiment of the presentinvention utilizing the stent 100 illustrated in FIG. 1. As illustrated,the stent 100 may be modified to comprise one or more reservoirs 106.Each of the reservoirs 106 may be opened or closed as desired. Thesereservoirs 106 may be specifically designed to hold the drug/drugcombinations to be delivered. Regardless of the design of the stent 100,it is preferable to have the drug/drug combination dosage applied withenough specificity and a sufficient concentration to provide aneffective dosage in the lesion area. In this regard, the reservoir sizein the bands 102 is preferably sized to adequately apply the drug/drugcombination dosage at the desired location and in the desired amount.

[0067] In an alternate exemplary embodiment, the entire inner and outersurface of the stent 100 may be coated with drug/drug combinations intherapeutic dosage amounts. A detailed description of a drug fortreating restenosis, as well as exemplary coating techniques, isdescribed below. It is, however, important to note that the coatingtechniques may vary depending on the drug/drug combinations. Also, thecoating techniques may vary depending on the material comprising thestent or other intraluminal medical device.

[0068] Rapamycin is a macrocyclic triene antibiotic produced byStreptomyces hygroscopicus as disclosed in U.S. Pat. No. 3,929,992. Ithas been found that rapamycin among other things inhibits theproliferation of vascular smooth muscle cells in vivo. Accordingly,rapamycin may be utilized in treating intimal smooth muscle cellhyperplasia, restenosis, and vascular occlusion in a mammal,particularly following either biologically or mechanically mediatedvascular injury, or under conditions that would predispose a mammal tosuffering such a vascular injury. Rapamycin functions to inhibit smoothmuscle cell proliferation and does not interfere with there-endothelialization of the vessel walls.

[0069] Rapamycin reduces vascular hyperplasia by antagonizing smoothmuscle proliferation in response to mitogenic signals that are releasedduring an angioplasty induced injury. Inhibition of growth factor andcytokine mediated smooth muscle proliferation at the late G1 phase ofthe cell cycle is believed to be the dominant mechanism of action ofrapamycin. However, rapamycin is also known to prevent T-cellproliferation and differentiation when administered systemically. Thisis the basis for its immunosuppresive activity and its ability toprevent graft rejection.

[0070] As used herein, rapamycin includes rapamycin and all analogs,derivatives and congeners that bind to FKBP12, and other immunophilinsand possesses the same pharmacologic properties as rapamycin includinginhibition of TOR.

[0071] Although the anti-proliferative effects of rapamycin may beachieved through systemic use, superior results may be achieved throughthe local delivery of the compound. Essentially, rapamycin works in thetissues, which are in proximity to the compound, and has diminishedeffect as the distance from the delivery device increases. In order totake advantage of this effect, one would want the rapamycin in directcontact with the lumen walls. Accordingly, in a preferred embodiment,the rapamycin is incorporated onto the surface of the stent or portionsthereof. Essentially, the rapamycin is preferably incorporated into thestent 100, illustrated in FIG. 1, where the stent 100 makes contact withthe lumen wall.

[0072] Rapamycin may be incorporated onto or affixed to the stent in anumber of ways. In the exemplary embodiment, the rapamycin is directlyincorporated into a polymeric matrix and sprayed onto the outer surfaceof the stent. The rapamycin elutes from the polymeric matrix over timeand enters the surrounding tissue. The rapamycin preferably remains onthe stent for at least three days up to approximately six months, andmore preferably between seven and thirty days.

[0073] Any number of non-erodible polymers may be utilized inconjunction with rapamycin. In one exemplary embodiment, the rapamycinor other therapeutic agent may be incorporated into a film-formingpolyfluoro copolymer comprising an amount of a first moiety selectedfrom the group consisting of polymerized vinylidenefluoride andpolymerized tetrafluoroethylene, and an amount of a second moiety otherthan the first moiety and which is copolymerized with the first moiety,thereby producing the polyfluoro copolymer, the second moiety beingcapable of providing toughness or elastomeric properties to thepolyfluoro copolymer, wherein the relative amounts of the first moietyand the second moiety are effective to provide the coating and filmproduced therefrom with properties effective for use in treatingimplantable medical devices.

[0074] The present invention provides polymeric coatings comprising apolyfluoro copolymer and implantable medical devices, for example,stents coated with a film of the polymeric coating in amounts effectiveto reduce thrombosis and/or restenosis when such stents are used in, forexample, angioplasty procedures. As used herein, polyfluoro copolymersmeans those copolymers comprising an amount of a first moiety selectedfrom the group consisting of polymerized vinylidenefluoride andpolymerized tetrafluoroethylene, and an amount of a second moiety otherthan the first moiety and which is copolymerized with the first moietyto produce the polyfluoro copolymer, the second moiety being capable ofproviding toughness or elastomeric properties to the polyfluorocopolymer, wherein the relative amounts of the first moiety and thesecond moiety are effective to provide coatings and film made from suchpolyfluoro copolymers with properties effective for use in coatingimplantable medical devices.

[0075] The coatings may comprise pharmaceutical or therapeutic agentsfor reducing restenosis, inflammation, and/or thrombosis, and stentscoated with such coatings may provide sustained release of the agents.Films prepared from certain polyfluoro copolymer coatings of the presentinvention provide the physical and mechanical properties required ofconventional coated medical devices, even where maximum temperature, towhich the device coatings and films are exposed, are limited torelatively low temperatures. This is particularly important when usingthe coating/film to deliver pharmaceutical/therapeutic agents or drugsthat are heat sensitive, or when applying the coating ontotemperature-sensitive devices such as catheters. When maximum exposuretemperature is not an issue, for example, where heat-stable agents suchas itraconazole are incorporated into the coatings, higher meltingthermoplastic polyfluoro copolymers may be used and, if very highelongation and adhesion is required, elastomers may be used. If desiredor required, the polyfluoro elastomers may be crosslinked by standardmethods described in, e.g., Modern Fluoropolymers, (J. Shires ed.), JohnWiley & Sons, New York, 1997, pp. 77-87.

[0076] The present invention comprises polyfluoro copolymers thatprovide improved biocompatible coatings or vehicles for medical devices.These coatings provide inert biocompatible surfaces to be in contactwith body tissue of a mammal, for example, a human, sufficient to reducerestenosis, or thrombosis, or other undesirable reactions. While manyreported coatings made from polyfluoro homopolymers are insoluble and/orrequire high heat, for example, greater than about one hundredtwenty-five degrees centigrade, to obtain films with adequate physicaland mechanical properties for use on implantable devices, for example,stents, or are not particularly tough or elastomeric, films preparedfrom the polyfluoro copolymers of the present invention provide adequateadhesion, toughness or elasticity, and resistance to cracking whenformed on medical devices. In certain exemplary embodiments, this is thecase even where the devices are subjected to relatively low maximumtemperatures.

[0077] The polyfluoro copolymers used for coatings according to thepresent invention are preferably film-forming polymers that havemolecular weight high enough so as not to be waxy or tacky. The polymersand films formed therefrom should preferably adhere to the stent and notbe readily deformable after deposition on the stent as to be able to bedisplaced by hemodynamic stresses. The polymer molecular weight shouldpreferably be high enough to provide sufficient toughness so that filmscomprising the polymers will not be rubbed off during handling ordeployment of the stent. In certain exemplary embodiments the coatingwill not crack where expansion of the stent or other medical devicesoccurs.

[0078] Coatings of the present invention comprise polyfluoro copolymers,as defined hereinabove. The second moiety polymerized with the firstmoiety to prepare the polyfluoro copolymer may be selected from thosepolymerized, biocompatible monomers that would provide biocompatiblepolymers acceptable for implantation in a mammal, while maintainingsufficient elastomeric film properties for use on medical devicesclaimed herein. Such monomers include, without limitation,hexafluoropropylene (HFP), tetrafluoroethylene (TFE),vinylidenefluoride, 1-hydropentafluoropropylene, perfluoro(methyl vinylether), chlorotrifluoroethylene (CTFE), pentafluoropropene,trifluoroethylene, hexafluoroacetone and hexafluoroisobutylene.

[0079] Polyfluoro copolymers used in the present invention typicallycomprise vinylidinefluoride copolymerized with hexafluoropropylene, inthe weight ratio in the range of from about fifty to about ninety-twoweight percent vinylidinefluoride to about fifty to about eight weightpercent HFP. Preferably, polyfluoro copolymers used in the presentinvention comprise from about fifty to about eighty-five weight percentvinylidinefluoride copolymerized with from about fifty to about fifteenweight percent HFP. More preferably, the polyfluoro copolymers willcomprise from about fifty-five to about seventy weight percentvinylidinefluoride copolymerized with from about forty-five to aboutthirty weight percent HFP. Even more preferably, polyfluoro copolymerscomprise from about fifty-five to about sixty-five weight percentvinylidinefluoride copolymerized with from about forty-five to aboutthirty-five weight percent HFP. Such polyfluoro copolymers are soluble,in varying degrees, in solvents such as dimethylacetamide (DMAc),tetrahydrofuran, dimethyl formamide, dimethyl sulfoxide and n-methylpyrrolidone. Some are soluble in methylethylketone (MEK), acetone,methanol and other solvents commonly used in applying coatings toconventional implantable medical devices.

[0080] Conventional polyfluoro homopolymers are crystalline anddifficult to apply as high quality films onto metal surfaces withoutexposing the coatings to relatively high temperatures that correspond tothe melting temperature (Tm) of the polymer. The elevated temperatureserves to provide films prepared from such PVDF homopolymer coatingsthat exhibit sufficient adhesion of the film to the device, whilepreferably maintaining sufficient flexibility to resist film crackingupon expansion/contraction of the coated medical device. Certain filmsand coatings according to the present invention provide these samephysical and mechanical properties, or essentially the same properties,even when the maximum temperatures to which the coatings and films areexposed is less than about a maximum predetermined temperature. This isparticularly important when the coatings/films comprise pharmaceuticalor therapeutic agents or drugs that are heat sensitive, for example,subject to chemical or physical degradation or other heat-inducednegative affects, or when coating heat sensitive substrates of medicaldevices, for example, subject to heat-induced compositional orstructural degradation.

[0081] Depending on the particular device upon which the coatings andfilms of the present invention are to be applied and the particularuse/result required of the device, polyfluoro copolymers used to preparesuch devices may be crystalline, semi-crystalline or amorphous.

[0082] Where devices have no restrictions or limitations with respect toexposure of same to elevated temperatures, crystalline polyfluorocopolymers may be employed. Crystalline polyfluoro copolymers tend toresist the tendency to flow under applied stress or gravity when exposedto temperatures above their glass transition (Tg) temperatures.Crystalline polyfluoro copolymers provide tougher coatings and filmsthan their fully amorphous counterparts. In addition, crystallinepolymers are more lubricious and more easily handled through crimpingand transfer processes used to mount self-expanding stents, for example,nitinol stents.

[0083] Semi-crystalline and amorphous polyfluoro copolymers areadvantageous where exposure to elevated temperatures is an issue, forexample, where heat-sensitive pharmaceutical or therapeutic agents areincorporated into the coatings and films, or where device design,structure and/or use preclude exposure to such elevated temperatures.Semi-crystalline polyfluoro copolymer elastomers comprising relativelyhigh levels, for example, from about thirty to about forty-five weightpercent of the second moiety, for example, HFP, copolymerized with thefirst moiety, for example, VDF, have the advantage of reducedcoefficient of friction and self-blocking relative to amorphouspolyfluoro copolymer elastomers. Such characteristics may be ofsignificant value when processing, packaging and delivering medicaldevices coated with such polyfluoro copolymers. In addition, suchpolyfluoro copolymer elastomers comprising such relatively high contentof the second moiety serves to control the solubility of certain agents,for example, rapamycin, in the polymer and therefore controlspermeability of the agent through the matrix.

[0084] Polyfluoro copolymers utilized in the present inventions may beprepared by various known polymerization methods. For example, highpressure, free-radical, semi-continuous emulsion polymerizationtechniques such as those disclosed in Fluoroelastomers-dependence ofrelaxation phenomena on compositions, POLYMER 30, 2180, 1989, byAjroldi, et al., may be employed to prepare amorphous polyfluorocopolymers, some of which may be elastomers. In addition, free-radicalbatch emulsion polymerization techniques disclosed herein may be used toobtain polymers that are semi-crystalline, even where relatively highlevels of the second moiety are included.

[0085] As described above, stents may comprise a wide variety ofmaterials and a wide variety of geometrics. Stents may be made ofbiocomptible materials, including biostable and bioabsorbable materials.Suitable biocompatible metals include, but are not limited to, stainlesssteel, tantalum, titanium alloys (including nitinol), and cobalt alloys(including cobalt-chromium nickel alloys). Suitable nonmetallicbiocompatible materials include, but are not limited to, polyamides,polyolefins (i.e. polypropylene, polyethylene etc.), nonabsorbablepolyesters (i.e. polyethylene terephthalate), and bioabsorbablealiphatic polyesters (i.e. homopolymers and copolymers of lactic acid,glycolic acid, lactide, glycolide, para-dioxanone, trimethylenecarbonate, caprolactone, and blends thereof).

[0086] The film-forming biocompatible polymer coatings generally areapplied to the stent in order to reduce local turbulence in blood flowthrough the stent, as well as adverse tissue reactions. The coatings andfilms formed therefrom also may be used to administer a pharmaceuticallyactive material to the site of the stent placement. Generally, theamount of polymer coating to be applied to the stent will vary dependingon, among other possible parameters, the particular polyfluoro copolymerused to prepare the coating, the stent design and the desired effect ofthe coating. Generally, the coated stent will comprise from about 0.1 toabout fifteen weight percent of the coating, preferably from about 0.4to about ten weight percent. The polyfluoro copolymer coatings may beapplied in one or more coating steps, depending on the amount ofpolyfluoro copolymer to be applied. Different polyfluoro copolymers maybe used for different layers in the stent coating. In fact, in certainexemplary embodiments, it is highly advantageous to use a diluted firstcoating solution comprising a polyfluoro copolymer as a primer topromote adhesion of a subsequent polyfluoro copolymer coating layer thatmay include pharmaceutically active materials. The individual coatingsmay be prepared from different polyfluoro copolymers.

[0087] Additionally, a top coating may be applied to delay release ofthe pharmaceutical agent, or they could be used as the matrix for thedelivery of a different pharmaceutically active material. Layering ofcoatings may be used to stage release of the drug or to control releaseof different agents placed in different layers.

[0088] Blends of polyfluoro copolymers may also be used to control therelease rate of different agents or to provide a desirable balance ofcoating properties, i.e. elasticity, toughness, etc., and drug deliverycharacteristics, for example, release profile. Polyfluoro copolymerswith different solubilities in solvents may be used to build updifferent polymer layers that may be used to deliver different drugs orto control the release profile of a drug. For example, polyfluorocopolymers comprising 85.5/14.5 (wt/wt) of poly(vinylidinefluoride/HFP)and 60.6/39.4 (wt/wt) of poly(vinylidinefluoride/HFP) are both solublein DMAc. However, only the 60.6/39.4 PVDF polyfluoro copolymer issoluble in methanol. So, a first layer of the 85.5/14.5 PVDF polyfluorocopolymer comprising a drug could be over coated with a topcoat of the60.6/39.4 PVDF polyfluoro copolymer made with the methanol solvent. Thetop coating may be used to delay the drug delivery of the drug containedin the first layer. Alternately, the second layer could comprise adifferent drug to provide for sequential drug delivery. Multiple layersof different drugs could be provided by alternating layers of first onepolyfluoro copolymer, then the other. As will be readily appreciated bythose skilled in the art, numerous layering approaches may be used toprovide the desired drug delivery.

[0089] Coatings may be formulated by mixing one or more therapeuticagents with the coating polyfluoro copolymers in a coating mixture. Thetherapeutic agent may be present as a liquid, a finely divided solid, orany other appropriate physical form. Optionally, the coating mixture mayinclude one or more additives, for example, nontoxic auxiliarysubstances such as diluents, carriers, excipients, stabilizers or thelike. Other suitable additives may be formulated with the polymer andpharmaceutically active agent or compound. For example, a hydrophilicpolymer may be added to a biocompatible hydrophobic coating to modifythe release profile, or a hydrophobic polymer may be added to ahydrophilic coating to modify the release profile. One example would beadding a hydrophilic polymer selected from the group consisting ofpolyethylene oxide, polyvinyl pyrrolidone, polyethylene glycol,carboxylmethyl cellulose, and hydroxymethyl cellulose to a polyfluorocopolymer coating to modify the release profile. Appropriate relativeamounts may be determined by monitoring the in vitro and/or in vivorelease profiles for the therapeutic agents.

[0090] The best conditions for the coating application are when thepolyfluoro copolymer and pharmaceutic agent have a common solvent. Thisprovides a wet coating that is a true solution. Less desirable, yetstill usable, are coatings that contain the pharmaceutical agent as asolid dispersion in a solution of the polymer in solvent. Under thedispersion conditions, care must be taken to ensure that the particlesize of the dispersed pharmaceutical powder, both the primary powdersize and its aggregates and agglomerates, is small enough not to causean irregular coating surface or to clog the slots of the stent that needto remain essentially free of coating. In cases where a dispersion isapplied to the stent and the smoothness of the coating film surfacerequires improvement, or to be ensured that all particles of the drugare fully encapsulated in the polymer, or in cases where the releaserate of the drug is to be slowed, a clear (polyfluoro copolymer only)topcoat of the same polyfluoro copolymer used to provide sustainedrelease of the drug or another polyfluoro copolymer that furtherrestricts the diffusion of the drug out of the coating may be applied.The topcoat may be applied by dip coating with mandrel to clear theslots. This method is disclosed in U.S. Pat. No. 6,153,252. Othermethods for applying the topcoat include spin coating and spray coating.Dip coating of the topcoat can be problematic if the drug is verysoluble in the coating solvent, which swells the polyfluoro copolymer,and the clear coating solution acts as a zero concentration sink andredissolves previously deposited drug. The time spent in the dip bathmay need to be limited so that the drug is not extracted out into thedrug-free bath. Drying should be rapid so that the previously depositeddrug does not completely diffuse into the topcoat.

[0091] The amount of therapeutic agent will be dependent upon theparticular drug employed and medical condition being treated. Typically,the amount of drug represents about 0.001 percent to about seventypercent of the total coating weight, more typically about 0.001 percentto about sixty percent of the total coating weight. It is possible thatthe drug may represent as little as 0.0001 percent to the total coatingweight.

[0092] The quantity and type of polyfluoro copolymers employed in thecoating film comprising the pharmaceutic agent will vary depending onthe release profile desired and the amount of drug employed. The productmay contain blends of the same or different polyfluoro copolymers havingdifferent molecular weights to provide the desired release profile orconsistency to a given formulation.

[0093] Polyfluoro copolymers may release dispersed drug by diffusion.This can result in prolonged delivery (over, say approximately one totwo-thousand hours, preferably two to eight-hundred hours) of effectiveamounts (0.001 μg/cm²-min to 1000 μg/cm²-m in) of the drug. The dosagemay be tailored to the subject being treated, the severity of theaffliction, the judgment of the prescribing physician, and the like.

[0094] Individual formulations of drugs and polyfluoro copolymers may betested in appropriate in vitro and in vivo models to achieve the desireddrug release profiles. For example, a drug could be formulated with apolyfluoro copolymer, or blend of polyfluoro copolymers, coated onto astent and placed in an agitated or circulating fluid system, forexample, twenty-five percent ethanol in water. Samples of thecirculating fluid could be taken to determine the release profile (suchas by HPLC, UV analysis or use of radiotagged molecules). The release ofa pharmaceutical compound from a stent coating into the interior wall ofa lumen could be modeled in appropriate animal system. The drug releaseprofile could then be monitored by appropriate means such as, by takingsamples at specific times and assaying the samples for drugconcentration (using HPLC to detect drug concentration). Thrombusformation can be modeled in animal models using the In-platelet imagingmethods described by Hanson and Harker, Proc. Natl. Acad. Sci. USA85:3184-3188 (1988). Following this or similar procedures, those skilledin the art will be able to formulate a variety of stent coatingformulations.

[0095] While not a requirement of the present invention, the coatingsand films may be crosslinked once applied to the medical devices.Crosslinking may be affected by any of the known crosslinkingmechanisms, such as chemical, heat or light. In addition, crosslinkinginitiators and promoters may be used where applicable and appropriate.In those exemplary embodiments utilizing crosslinked films comprisingpharmaceutical agents, curing may affect the rate at which the drugdiffuses from the coating. Crosslinked polyfluoro copolymers films andcoatings of the present invention also may be used without drug tomodify the surface of implantable medical devices.

EXAMPLES Example 1

[0096] A PVDF homopolymer (Solef® 1008 from Solvay Advanced Polymers,Houston, Tex., Tm about 175° C.) and polyfluoro copolymers ofpoly(vinylidenefluoride/HFP), 92/8 and 91/9 weight percentvinylidenefluoride/HFP as determined by F¹⁹ NMR, respectively (eg:Solef® 11010 and 11008, Solvay Advanced Polymers, Houston, Tex., Tmabout 159 degrees C. and 160 degrees C., respectively) were examined aspotential coatings for stents. These polymers are soluble in solventssuch as, but not limited to, DMAc, N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), N-methylpyrrolidone (NMP), tetrahydrofuran (THF) andacetone. Polymer coatings were prepared by dissolving the polymers inacetone, at five weight percent as a primer, or by dissolving thepolymer in 50/50 DMAc/acetone, at thirty weight percent as a topcoat.Coatings that were applied to the stents by dipping and dried at 60degrees C. in air for several hours, followed by 60 degrees C. for threehours in a <100 mm Hg vacuum, resulted in white foamy films. As applied,these films adhered poorly to the stent and flaked off, indicating theywere too brittle. When stents coated in this manner were heated above175 degrees C., i.e. above the melting temperature of the polymer, aclear, adherent film was formed. Since coatings require hightemperatures, for example, above the melting temperature of the polymer,to achieve high quality films. As mentioned above, the high temperatureheat treatment is unacceptable for the majority of drug compounds due totheir thermal sensitivity.

Example 2

[0097] A polyfluoro copolymer (Solef® 21508) comprising 85.5 weightpercent vinylidenefluoride copolymerized with 14.5 weight percent HFP,as determined by F¹⁹ NMR, was evaluated. This copolymer is lesscrystalline than the polyfluoro homopolymer and copolymers described inExample 1. It also has a lower melting point reported to be about 133degrees C. Once again, a coating comprising about twenty weight percentof the polyfluoro copolymer was applied from a polymer solution in 50/50DMAc/MEK. After drying (in air) at 60 degrees C. for several hours,followed by 60 degrees C. for three hours in a <100 mtorr Hg vacuum,clear adherent films were obtained. This eliminated the need for a hightemperature heat treatment to achieve high quality films. Coatings weresmoother and more adherent than those of Example 1. Some coated stentsthat underwent expansion show some degree of adhesion loss and “tenting”as the film pulls away from the metal. Where necessary, modification ofcoatings containing such copolymers may be made, e.g. by addition ofplasticizers or the like to the coating compositions. Films preparedfrom such coatings may be used to coat stents or other medical devices,particularly where those devices are not susceptible to expansion to thedegree of the stents.

[0098] The coating process above was repeated, this time with a coatingcomprising the 85.5/14.6 (wt/wt) (vinylidenefluoride/HFP) and aboutthirty weight percent of rapamycin (Wyeth-Ayerst Laboratories,Philadelphia, Pa.), based on total weight of coating solids. Clear filmsthat would occasionally crack or peel upon expansion of the coatedstents resulted. It is believed that inclusion of plasticizers and thelike in the coating composition will result in coatings and films foruse on stents and other medical devices that are not susceptible to suchcracking and peeling.

Example 3

[0099] Polyfluoro copolymers of still higher HFP content were thenexamined. This series of polymers were not semicrystalline, but ratherare marketed as elastomers. One such copolymer is Fluorel™ FC2261Q (fromDyneon, a 3M-Hoechst Enterprise, Oakdale, Minn.), a 60.6/39.4 (wt/wt)copolymer of vinylidenefluoride/HFP. Although this copolymer has a Tgwell below room temperature (Tg about minus twenty degrees C.) it is nottacky at room temperature or even at sixty degrees C. This polymer hasno detectable crystallinity when measured by Differential ScanningCalorimetry (DSC) or by wide angle X-ray diffraction. Films formed onstents as described above were non-tacky, clear, and expanded withoutincident when the stents were expanded.

[0100] The coating process above was repeated, this time with coatingscomprising the 60.6/39.4 (wt/wt) (vinylidenefluoride/HFP) and aboutnine, thirty and fifty weight percent of rapamycin (Wyeth-AyerstLaboratories, Philadelphia, Pa.), based on total weight of coatingsolids, respectively. Coatings comprising about nine and thirty weightpercent rapamycin provided white, adherent, tough films that expandedwithout incident on the stent. Inclusion of fifty percent drug, in thesame manner, resulted in some loss of adhesion upon expansion.

[0101] Changes in the comonomer composition of the polyfluoro copolymeralso can affect the nature of the solid state coating, once dried. Forexample, the semicrystalline copolymer, Solef® 21508, containing 85.5percent vinylidenefluoride polymerized with 14.5 percent by weight HFPforms homogeneous solutions with about 30 percent rapamycin (drug weightdivided by total solids weight, for example, drug plus copolymer) inDMAc and 50/50 DMAc/MEK. When the film is dried (60 degrees C./16 hoursfollowed by 60 degrees C./3 hours in vacuum of 100 mm Hg) a clearcoating, indicating a solid solution of the drug in the polymer, isobtained. Conversely, when an amorphous copolymer, Fluorel™ FC2261Q, ofPDVF/HFP at 60.6/39.5 (wt/wt) forms a similar thirty percent solution ofrapamycin in DMAc/MEK and is similarly dried, a white film, indicatingphase separation of the drug and the polymer, is obtained. This seconddrug containing film is much slower to release the drug into an in vitrotest solution of twenty-five percent ethanol in water than is the formerclear film of crystalline Solef® 21508. X-ray analysis of both filmsindicates that the drug is present in a non-crystalline form. Poor orvery low solubility of the drug in the high HFP containing copolymerresults in slow permeation of the drug through the thin coating film.Permeability is the product of diffusion rate of the diffusing species(in this case the drug) through the film (the copolymer) and thesolubility of the drug in the film.

Example 4 In Vitro Release Results of Rapamycin from Coating

[0102]FIG. 3 is a plot of data for the 85.5/14.5 vinylidenefluoride/HFPpolyfluoro copolymer, indicating fraction of drug released as a functionof time, with no topcoat. FIG. 4 is a plot of data for the samepolyfluoro copolymer over which a topcoat has been disposed, indicatingthat most effect on release rate is with a clear topcoat. As showntherein, TC150 refers to a device comprising one hundred fiftymicrograms of topcoat, TC235 refers to two hundred thirty-fivemicrograms of topcoat, etc. The stents before topcoating had an averageof seven hundred fifty micrograms of coating containing thirty percentrapamycin. FIG. 5 is a plot for the 60.6/39.4 vinylidenefluoride/HFPpolyfluoro copolymer, indicating fraction of drug released as a functionof time, showing significant control of release rate from the coatingwithout the use of a topcoat. Release is controlled by loading of drugin the film.

Example 5 In Vivo Stent Release Kinetics of Rapamycin from Poly(VDF/HFP)

[0103] Nine New Zealand white rabbits (2.5-3.0 kg) on a normal diet weregiven aspirin twenty-four hours prior to surgery, again just prior tosurgery and for the remainder of the study. At the time of surgery,animals were premedicated with Acepromazine (0.1-0.2 mg/kg) andanesthetized with a Ketamine/Xylazine mixture (40 mg/kg and 5 mg/kg,respectively). Animals were given a single intraprocedural dose ofheparin (150 IU/kg, i.v.)

[0104] Arteriectomy of the right common carotid artery was performed anda 5 F catheter introducer (Cordis, Inc.) placed in the vessel andanchored with ligatures. Iodine contrast agent was injected to visualizethe right common carotid artery, brachlocephalic trunk and aortic arch.A steerable guide wire (0.014 inch/180 cm, Cordis, Inc.) was insertedvia the introducer and advanced sequentially into each iliac artery to alocation where the artery possesses a diameter closest to 2 mm using theangiographic mapping done previously. Two stents coated with a film madeof poly(VDF/HFP):(60.6/39.4) with thirty percent rapamycin were deployedin each animal where feasible, one in each iliac artery, using 3.0 mmballoon and inflation to 8-10 ATM for thirty seconds followed after aone minute interval by a second inflation to 8-10 ATM for thirtyseconds. Follow-up angiographs visualizing both iliac arteries areobtained to confirm correct deployment position of the stent.

[0105] At the end of procedure, the carotid artery was ligated and theskin is closed with 3/0 vicryl suture using a one layered interruptedclosure. Animals were given butoropanol (0.4 mg/kg, s.c.) and gentamycin(4 mg/kg, i.m.). Following recovery, the animals were returned to theircages and allowed free access to food and water.

[0106] Due to early deaths and surgical difficulties, two animals werenot used in this analysis. Stented vessels were removed from theremaining seven animals at the following time points: one vessel (oneanimal) at ten minutes post implant; six vessels (three animals) betweenforty minutes and two hours post-implant (average, 1.2 hours); twovessels (two animals) at three days post implant; and two vessels (oneanimal) at seven days post-implant. In one animal at two hours, thestent was retrieved from the aorta rather than the iliac artery. Uponremoval, arteries were carefully trimmed at both the proximal and distalends of the stent. Vessels were then carefully dissected free of thestent, flushed to remove any residual blood, and both stent and vesselfrozen immediately, wrapped separately in foil, labeled and kept frozenat minus eighty degrees C. When all samples had been collected, vesselsand stents were frozen, transported and subsequently analyzed forrapamycin in tissue and results are illustrated in FIG. 4.

Example 6 Purifying the Polymer

[0107] The Fluorel™ FC2261Q copolymer was dissolved in MEK at about tenweight percent and was washed in a 50/50 mixture of ethanol/water at a14:1 of ethanol/water to MEK solution ratio. The polymer precipitatedout and was separated from the solvent phase by centrifugation. Thepolymer again was dissolved in MEK and the washing procedure repeated.The polymer was dried after each washing step at sixty degrees C. in avacuum oven (<200 mtorr) over night.

Example 7 In Vivo Testing of Coated Stents in Porcine Coronary Arteries

[0108] CrossFlex® stents (available from Cordis, a Johnson & JohnsonCompany) were coated with the “as received” Fluorel™ FC2261Q PVDFcopolymer and with the purified polyfluoro copolymer of Example 6, usingthe dip and wipe approach. The coated stents were sterilized usingethylene oxide and a standard cycle. The coated stents and bare metalstents (controls) were implanted in porcine coronary arteries, wherethey remained for twenty-eight days.

[0109] Angiography was performed on the pigs at implantation and attwenty-eight days. Angiography indicated that the control uncoated stentexhibited about twenty-one percent restenosis. The polyfluoro copolymer“as received” exhibited about twenty-six percent restenosis (equivalentto the control) and the washed copolymer exhibited about 12.5 percentrestenosis.

[0110] Histology results reported neointimal area at twenty-eight daysto be 2.89±0.2, 3.57+0.4 and 2.75+0.3, respectively, for the bare metalcontrol, the unpurified copolymer and the purified copolymer.

[0111] Since rapamycin acts by entering the surrounding tissue, it ispreferably only affixed to the surface of the stent making contact withone tissue. Typically, only the outer surface of the stent makes contactwith the tissue. Accordingly, in one exemplary embodiment, only theouter surface of the stent is coated with rapamycin.

[0112] The circulatory system, under normal conditions, has to beself-sealing, otherwise continued blood loss from an injury would belife threatening. Typically, all but the most catastrophic bleeding israpidly stopped though a process known as hemostasis. Hemostasis occursthrough a progression of steps. At high rates of flow, hemostasis is acombination of events involving platelet aggregation and fibrinformation. Platelet aggregation leads to a reduction in the blood flowdue to the formation of a cellular plug while a cascade of biochemicalsteps leads to the formation of a fibrin clot.

[0113] Fibrin clots, as stated above, form in response to injury. Thereare certain circumstances where blood clotting or clotting in a specificarea may pose a health risk. For example, during percutaneoustransluminal coronary angioplasty, the endothelial cells of the arterialwalls are typically injured, thereby exposing the sub-endothelial cells.Platelets adhere to these exposed cells. The aggregating platelets andthe damaged tissue initiate further biochemical process resulting inblood coagulation. Platelet and fibrin blood clots may prevent thenormal flow of blood to critical areas. Accordingly, there is a need tocontrol blood clotting in various medical procedures. Compounds that donot allow blood to clot are called anti-coagulants. Essentially, ananti-coagulant is an inhibitor of thrombin formation or function. Thesecompounds include drugs such as heparin and hirudin. As used herein,heparin includes all direct or indirect inhibitors of thrombin or FactorXa.

[0114] In addition to being an effective anti-coagulant, heparin hasalso been demonstrated to inhibit smooth muscle cell growth in vivo.Thus, heparin may be effectively utilized in conjunction with rapamycinin the treatment of vascular disease. Essentially, the combination ofrapamycin and heparin may inhibit smooth muscle cell growth via twodifferent mechanisms in addition to the heparin acting as ananti-coagulant.

[0115] Because of its multifunctional chemistry, heparin may beimmobilized or affixed to a stent in a number of ways. For example,heparin may be immobilized onto a variety of surfaces by variousmethods, including the photolink methods set forth in U.S. Pat. Nos.3,959,078 and 4,722,906 to Guire et al. and U.S. Pat. Nos. 5,229,172;5,308,641; 5,350,800 and 5,415,938 to Cahalan et al. Heparinizedsurfaces have also been achieved by controlled release from a polymermatrix, for example, silicone rubber, as set forth in U.S. Pat. Nos.5,837,313; 6,099,562 and 6,120,536 to Ding et al.

[0116] Unlike rapamycin, heparin acts on circulating proteins in theblood and heparin need only make contact with blood to be effective.Accordingly, if used in conjunction with a medical device, such as astent, it would preferably be only on the side that comes into contactwith the blood. For example, if heparin were to be administered via astent, it would only have to be on the inner surface of the stent to beeffective.

[0117] In an exemplary embodiment of the invention, a stent may beutilized in combination with rapamycin and heparin to treat vasculardisease. In this exemplary embodiment, the heparin is immobilized to theinner surface of the stent so that it is in contact with the blood andthe rapamycin is immobilized to the outer surface of the stent so thatit is in contact with the surrounding tissue. FIG. 7 illustrates across-section of a band 102 of the stent 100 illustrated in FIG. 1. Asillustrated, the band 102 is coated with heparin 108 on its innersurface 110 and with rapamycin 112 on its outer surface 114.

[0118] In an alternate exemplary embodiment, the stent may comprise aheparin layer immobilized on its inner surface, and rapamycin andheparin on its outer surface. Utilizing current coating techniques,heparin tends to form a stronger bond with the surface it is immobilizedto then does rapamycin. Accordingly, it may be possible to firstimmobilize the rapamycin to the outer surface of the stent and thenimmobilize a layer of heparin to the rapamycin layer. In thisembodiment, the rapamycin may be more securely affixed to the stentwhile still effectively eluting from its polymeric matrix, through theheparin and into the surrounding tissue. FIG. 8 illustrates across-section of a band 102 of the stent 100 illustrated in FIG. 1. Asillustrated, the band 102 is coated with heparin 108 on its innersurface 110 and with rapamycin 1112 and heparin 108 on its outer surface114.

[0119] There are a number of possible ways to immobilize, i.e.,entrapment or covalent linkage with an erodible bond, the heparin layerto the rapamycin layer. For example, heparin may be introduced into thetop layer of the polymeric matrix. In other embodiments, different formsof heparin may be directly immobilized onto the top coat of thepolymeric matrix, for example, as illustrated in FIG. 9. As illustrated,a hydrophobic heparin layer 116 may be immobilized onto the top coatlayer 118 of the rapamycin layer 112. A hydrophobic form of heparin isutilized because rapamycin and heparin coatings represent incompatiblecoating application technologies. Rapamycin is an organic solvent-basedcoating and heparin, in its native form, is a water-based coating.

[0120] As stated above, a rapamycin coating may be applied to stents bya dip, spray or spin coating method, and/or any combination of thesemethods. Various polymers may be utilized. For example, as describedabove, poly(ethylene-co-vinyl acetate) and polybutyl methacrylate blendsmay be utilized. Other polymers may also be utilized, but not limitedto, for example, polyvinylidene fluoride-co-hexafluoropropylene andpolyethylbutyl methacrylate-co-hexyl methacrylate. Also as describedabove, barrier or top coatings may also be applied to modulate thedissolution of rapamycin from the polymer matrix. In the exemplaryembodiment described above, a thin layer of heparin is applied to thesurface of the polymeric matrix. Because these polymer systems arehydrophobic and incompatible with the hydrophilic heparin, appropriatesurface modifications may be required.

[0121] The application of heparin to the surface of the polymeric matrixmay be performed in various ways and utilizing various biocompatiblematerials. For example, in one embodiment, in water or alcoholicsolutions, polyethylene imine may be applied on the stents, with carenot to degrade the rapamycin (e.g., pH <7, low temperature), followed bythe application of sodium heparinate in aqueous or alcoholic solutions.As an extension of this surface modification, covalent heparin may belinked on polyethylene imine using amide-type chemistry (using acarbondiimide activator, e.g. EDC) or reductive amination chemistry(using CBAS-heparin and sodium cyanoborohydride for coupling). Inanother exemplary embodiment, heparin may be photolinked on the surface,if it is appropriately grafted with photo initiator moieties. Uponapplication of this modified heparin formulation on the covalent stentsurface, light exposure causes cross-linking and immobilization of theheparin on the coating surface. In yet another exemplary embodiment,heparin may be complexed with hydrophobic quaternary ammonium salts,rendering the molecule soluble in organic solvents (e.g. benzalkoniumheparinate, troidodecylmethylammonium heparinate). Such a formulation ofheparin may be compatible with the hydrophobic rapamycin coating, andmay be applied directly on the coating surface, or in therapamycin/hydrophobic polymer formulation.

[0122] It is important to note that the stent, as described above, maybe formed from any number of materials, including various metals,polymeric materials and ceramic materials. Accordingly, varioustechnologies may be utilized to immobilize the various drugs, agent,compound combinations thereon. Specifically, in addition to thepolymeric matricies described above biopolymers may be utilized.Biopolymers may be generally classified as natural polymers, while theabove-described polymers may be described as synthetic polymers.Exemplary biopolymers, which may be utilized include, agarose, alginate,gelatin, collagen and elastin. In addition, the drugs, agents orcompounds may be utilized in conjunction with other percutaneouslydelivered medical devices such as grafts and profusion balloons.

[0123] In addition to utilizing an anti-proliferative andanti-coagulant, anti-inflammatories may also be utilized in combinationtherewith. One example of such a combination would be the addition of ananti-inflammatory corticosteroid such as dexamethasone with ananti-proliferative, such as rapamycin, cladribine, vincristine, taxol,or a nitric oxide donor and an anti-coagulant, such as heparin. Suchcombination therapies might result in a better therapeutic effect, i.e.,less proliferation as well as less inflammation, a stimulus forproliferation, than would occur with either agent alone. The delivery ofa stent comprising an anti-proliferative, anti-coagulant, and ananti-inflammatory to an injured vessel would provide the addedtherapeutic benefit of limiting the degree of local smooth muscle cellproliferation, reducing a stimulus for proliferation, i.e., inflammationand reducing the effects of coagulation thus enhancing therestenosis-limiting action of the stent.

[0124] In other exemplary embodiments of the inventions, growth factorinhibitor or cytokine signal transduction inhibitor, such as the rasinhibitor, R 15777, or P38 kinase inhibitor, RWJ67657, or a tyrosinekinase inhibitor, such as tyrphostin, might be combined with ananti-proliferative agent such as taxol, vincristine or rapamycin so thatproliferation of smooth muscle cells could be inhibited by differentmechanisms. Alternatively, an anti-proliferative agent such as taxol,vincristine or rapamycin could be combined with an inhibitor ofextracellular matrix synthesis such as halofuginone. In the above cases,agents acting by different mechanisms could act synergistically toreduce smooth muscle cell proliferation and vascular hyperplasia. Thisinvention is also intended to cover other combinations of two or moresuch drug agents. As mentioned above, such drugs, agents or compoundscould be administered systemically, delivered locally via drug deliverycatheter, or formulated for delivery from the surface of a stent, orgiven as a combination of systemic and local therapy.

[0125] In addition to anti-proliferatives, anti-inflammatories andanti-coagulants, other drugs, agents or compounds may be utilized inconjunction with the medical devices. For example, immunosuppressantsmay be utilized alone or in combination with these other drugs, agentsor compounds. Also gene therapy delivery mechanisms such as modifiedgenes (nucleic acids including recombinant DNA) in viral vectors andnon-viral gene vectors such as plasmids may also be introduced locallyvia a medical device. In addition, the present invention may be utilizedwith cell based therapy.

[0126] In addition to all of the drugs, agents, compounds and modifiedgenes described above, chemical agents that are not ordinarilytherapeutically or biologically active may also be utilized inconjunction with the present invention. These chemical agents, commonlyreferred to as pro-drugs, are agents that become biologically activeupon their introduction into the living organism by one or moremechanisms. These mechanisms include the addition of compounds suppliedby the organism or the cleavage of compounds from the agents caused byanother agent supplied by the organism. Typically, pro-drugs are moreabsorbable by the organism. In addition, pro-drugs may also provide someadditional measure of time release.

[0127] The coatings and drugs, agents or compounds described above maybe utilized in combination with any number of medical devices, and inparticular, with implantable medical devices such as stents andstent-grafts. Other devices such as vena cava filters and anastomosisdevices may be used with coatings having drugs, agents or compoundstherein. The exemplary stent illustrated in FIGS. 1 and 2 is a balloonexpandable stent. Balloon expandable stents may be utilized in anynumber of vessels or conduits, and are particularly well suited for usein coronary arteries. Self-expanding stents, on the other hand, areparticularly well suited for use in vessels where crush recovery is acritical factor, for example, in the carotid artery. Accordingly, it isimportant to note that any of the drugs, agents or compounds, as well asthe coatings described above, may be utilized in combination withself-expanding stents which are known in the art.

[0128] Anastomosis is the surgical joining of biological tissues,specifically the joining of tubular organs to create anintercommunication between them. Vascular surgery often involvescreating an anastomosis between blood vessels or between a blood vesseland a vascular graft to create or restore a blood flow path to essentialtissues. Coronary artery bypass graft surgery (CABG) is a surgicalprocedure to restore blood flow to ischemic heart muscle whose bloodsupply has been compromised by occlusion or stenosis of one or more ofthe coronary arteries. One method for performing CABG surgery involvesharvesting a saphenous vein or other venous or arterial conduit fromelsewhere in the body, or using an artificial conduit, such as one madeof Dacron®) or Goretex® tubing, and connecting this conduit as a bypassgraft from a viable artery, such as the aorta, to the coronary arterydownstream of the blockage or narrowing. A graft with both the proximaland distal ends of the graft detached is known as a “free graft.” Asecond method involves rerouting a less essential artery, such as theinternal mammary artery, from its native location so that it may beconnected to the coronary artery downstream of the blockage. Theproximal end of the graft vessel remains attached in its nativeposition. This type of graft is known as a “pedicled graft.” In thefirst case, the bypass graft must be attached to the native arteries byan end-to-side anastomosis at both the proximal and distal ends of thegraft. In the second technique at least one end-to-side anastomosis mustbe made at the distal end of the artery used for the bypass. In thedescription of the exemplary embodiment given below reference will bemade to the anastomoses on a free graft as the proximal anastomosis andthe distal anastomosis. A proximal anastomosis is an anastomosis on theend of the graft vessel connected to a source of blood, for example, theaorta and a distal anastomosis is an anastomosis on the end of the graftvessel connected to the destination of the blood flowing through it, forexample, a coronary artery. The anastomoses will also sometimes becalled the first anastomosis or second anastomosis, which refers to theorder in which the anastomoses are performed regardless of whether theanastomosis is on the proximal or distal end of the graft.

[0129] At present, essentially all vascular anastomoses are performed byconventional hand suturing. Suturing the anastomoses is a time-consumingand difficult task, requiring much skill and practice on the part of thesurgeon. It is important that each anastomosis provide a smooth, openflow path for the blood and that the attachment be completely free ofleaks. A completely leak-free seal is not always achieved on the veryfirst try. Consequently, there is a frequent need for resuturing of theanastomosis to close any leaks that are detected.

[0130] The time consuming nature of hand sutured anastomoses is ofspecial concern in CABG surgery for several reasons. Firstly, thepatient is required to be supported on cardiopulmonary bypass (CPB) formost of the surgical procedure, the heart must be isolated from thesystemic circulation (i.e. “cross-clamped”), and the heart must usuallybe stopped, typically by infusion of cold cardioplegia solution, so thatthe anastomosis site on the heart is still and blood-free during thesuturing of the anastomosis. Cardiopulminary bypass, circulatoryisolation and cardiac arrest are inherently very traumatic, and it hasbeen found that the frequency of certain post-surgical complicationsvaries directly with the duration for which the heart is undercardioplegic arrest (frequently referred to as the “crossclamp time”).Secondly, because of the high cost of cardiac operating room time, anyprolongation of the surgical procedure can significantly increase thecost of the bypass operation to the hospital and to the patient. Thus,it is desirable to reduce the duration of the crossclamp time and of theentire surgery by expediting the anastomosis procedure without reducingthe quality or effectiveness of the anastomoses.

[0131] The already high degree of manual skill required for conventionalmanually sutured anastomoses is even more elevated for closed-chest orport-access thoracoscopic bypass surgery, a newly developed surgicalprocedure designed to reduce the morbidity of CABG surgery as comparedto the standard open-chest CABG procedure. In the closed-chestprocedure, surgical access to the heart is made through narrow accessports made in the intercostal spaces of the patient's chest, and theprocedure is performed under thoracoscopic observation. Because thepatient's chest is not opened, the suturing of the anastomoses must beperformed at some distance, using elongated instruments positionedthrough the access ports for approximating the tissues and for holdingand manipulating the needles and sutures used to make the anastomoses.This requires even greater manual skill than the already difficultprocedure of suturing anastomoses during open-chest CABG surgery.

[0132] In order to reduce the difficulty of creating the vascularanastomoses during either open or closed-chest CABG surgery, it would bedesirable to provide a rapid means for making a reliable end-to-sideanastomosis between a bypass graft or artery and the aorta or the nativevessels of the heart. A first approach to expediting and improvinganastomosis procedures has been through stapling technology. Staplingtechnology has been successfully employed in many different areas ofsurgery for making tissue attachments faster and more reliably. Thegreatest progress in stapling technology has been in the area ofgastrointestinal surgery. Various surgical stapling instruments havebeen developed for end-to-end, side-to-side, and end-to-side anastomosesof hollow or tubular organs, such as the bowel. These instruments,unfortunately, are not easily adaptable for use in creating vascularanastomoses. This is partially due to the difficulty in miniaturizingthe instruments to make them suitable for smaller organs such as bloodvessels. Possibly even more important is the necessity of providing asmooth, open flow path for the blood. Known gastrointestinal staplinginstruments for end-to-side or end-to-end anastomosis of tubular organsare designed to create an inverted anastomosis, that is, one where thetissue folds inward into the lumen of the organ that is being attached.This is acceptable in gastrointestinal surgery, where it is mostimportant to approximate the outer layers of the intestinal tract (theserosa). This is the tissue which grows together to form a strong,permanent connection. However, in vascular surgery this geometry isunacceptable for several reasons. Firstly, the inverted vessel wallswould cause a disruption in the blood flow. This could cause decreasedflow and ischemia downstream of the disruption, or, worse yet, the flowdisruption or eddies created could become a locus for thrombosis whichcould shed emboli or occlude the vessel at the anastomosis site.Secondly, unlike the intestinal tract, the outer surfaces of the bloodvessels (the adventitia) will not grow together when approximated. Thesutures, staples, or other joining device may therefore be neededpermanently to maintain the structural integrity of the vascularanastomosis. Thirdly, to establish a permanent, nonthrombogenic vessel,the innermost layer (the endothelium) should grow together for acontinuous, uninterrupted lining of the entire vessel. Thus, it would bepreferable to have a stapling instrument that would create vascularanastomoses that are everted, that is folded outward, or which createdirect edge-to-edge coaptation without inversion.

[0133] At least one stapling instrument has been applied to performingvascular anastomoses during CABG surgery. This device, first adapted foruse in CABG surgery by Dr. Vasilii I. Kolesov and later refined by Dr.Evgenii V. Kolesov (U.S. Pat. No. 4,350,160), was used to create anend-to-end anastomosis between the internal mammary artery (IMA) or avein graft and one of the coronary arteries, primarily the left anteriordescending coronary artery (LAD). Because the device could only performend-to-end anastomoses, the coronary artery first had to be severed anddissected from the surrounding myocardium, and the exposed end evertedfor attachment. This technique limited the indications of the device tocases where the coronary artery was totally occluded, and thereforethere was no loss of blood flow by completely severing the coronaryartery downstream of the blockage to make the anastomosis. Consequently,this device is not applicable where the coronary artery is onlypartially occluded and is not at all applicable to making the proximalside-to-end anastomosis between a bypass graft and the aorta.

[0134] One attempt to provide a vascular stapling device for end-to-sidevascular anastomoses is described in U.S. Pat. No. 5,234,447, issued toKaster et al. for a Side-to-end Vascular Anastomotic Staple Apparatus.Kaster et al. provide a ring-shaped staple with staple legs extendingfrom the proximal and distal ends of the ring to join two blood vesselstogether in an end-to-side anastomosis. However, Kaster et al. does notprovide a complete system for quickly and automatically performing ananastomosis. The method of applying the anastomosis staple disclosed byKaster et al. involves a great deal of manual manipulation of thestaple, using hand operated tools to individually deform the distaltines of the staple after the graft has been attached and before it isinserted into the opening made in the aortic wall. One of the moredifficult maneuvers in applying the Kaster et al. staple involvescarefully everting the graft vessel over the sharpened ends of thestaple legs, then piercing the evened edge of the vessel with the staplelegs. Experimental attempts to apply this technique have proven to bevery problematic because of difficulty in manipulating the graft vesseland the potential for damage to the graft vessel wall. For speed,reliability and convenience, it is preferable to avoid the need forcomplex maneuvers while performing the anastomosis. Further bendingoperations must then be performed on the staple legs. Once the distaltines of the staple have been deformed, it may be difficult to insertthe staple through the aortotomy opening. Another disadvantage of theKaster et al. device is that the distal tines of the staple pierce thewall of the graft vessel at the point where it is evened over thestaple. Piercing the wall of the graft vessel potentially invitesleaking of the anastomosis and may compromise the structural integrityof the graft vessel wall, serving as a locus for a dissection or even atear which could lead to catastrophic failure. Because the Kaster et alstaple legs only apply pressure to the anastomosis at selected points,there is a potential for leaks between the staple legs. The distal tinesof the staple are also exposed to the blood flow path at the anastomoticsite where it is most critical to avoid the potential for thrombosis.There is also the potential that exposure of the medial layers of thegraft vessel where the staple pierces the wall could be a site for theonset of intimal hyperplasia, which would compromise the long-termpatency of the graft as described above. Because of these potentialdrawbacks, it is desirable to make the attachment to the graft vessel asatraumatic to the vessel wall as possible and to eliminate as much aspossible the exposure of any foreign materials or any vessel layersother than a smooth uninterrupted intimal layer within the anastomosissite or within the graft vessel lumen.

[0135] A second approach to expediting and improving anastomosisprocedures is through the use of anastomotic fittings for joining bloodvessels together. One attempt to provide a vascular anastomotic fittingdevice for end-to-side vascular anastomoses is described in U.S. Pat.No. 4,366,819, issued to Kaster for an Anastomotic Fitting. This deviceis a four-part anastomotic fitting having a tubular member over whichthe graft vessel is evened, a ring flange which engages the aortic wallfrom within the aortic lumen, and a fixation ring and a locking ringwhich engage the exterior of the aortic wall. Another similarAnastomotic Fitting is described in U.S. Pat. No. 4,368,736, also issuedto Kaster. This device is a tubular fitting with a flanged distal endthat fastens to the aortic wall with an attachment ring, and a proximalend with a graft fixation collar for attaching to the graft vessel.These devices have a number of drawbacks. Firstly, the anastomoticfittings described expose the foreign material of the anastomotic deviceto the blood flow path within the arteries. This is undesirable becauseforeign materials within the blood flow path can have a tendency tocause hemolysis, platelet deposition and thrombosis. Immune responses toforeign material, such as rejection of the foreign material orauto-immune responses triggered by the presence of foreign material,tend to be stronger when the material is exposed to the bloodstream. Assuch, it is preferable that as much as possible of the interior surfacesof an anastomotic fitting that will be exposed to the blood flow path becovered with vascular tissue, either from the target vessel or from thegraft vessel, so that a smooth, continuous, hemocompatible endotheliallayer will be presented to the bloodstream. The anastomotic fittingdescribed by Kaster in the '819 patent also has the potential drawbackthat the spikes that hold the graft vessel onto the anastomotic fittingare very close to the blood flow path, potentially causing trauma to theblood vessel that could lead to leaks in the anastomosis or compromiseof the mechanical integrity of the vessels. Consequently, it isdesirable to provide an anastomosis fitting that is as atraumatic to thegraft vessel as possible. Any sharp features such as attachment spikesshould be placed as far away from the blood flow path and theanastomosis site as possible so that there is no compromise of theanastomosis seal or the structural integrity of the vessels.

[0136] Another device, the 3M-Unilink device for end-to-end anastomosis(U.S. Pat. Nos. 4,624,257; 4,917,090; 4,917,091) is designed for use inmicrosurgery, such as for reattaching vessels severed in accidents. Thisdevice provides an anastomosis clamp that has two eversion rings whichare locked together by a series of impaling spikes on their opposingfaces. However, this device is awkward for use in end-to-sideanastomosis and tends to deform the target vessel; therefore it is notcurrently used in CABG surgery. Due to the delicate process needed toinsert the vessels into the device, it would also be unsuitable forport-access surgery.

[0137] In order to solve these and other problems, it is desirable toprovide an anastomosis device which performs an end-to-side anastomosisbetween blood vessels or other hollow organs and vessels. It is alsodesirable to provide an anastomosis device which minimizes the trauma tothe blood vessels while performing the anastomosis, which minimizes theamount of foreign materials exposed to the blood flow path within theblood vessels and which avoids leakage problems, and which promotesrapid endothelialization and healing. It is also desirable that theinvention provide a complete system for quickly and automaticallyperforming an anastomosis with a minimal amount of manual manipulation.

[0138] Anastomosis devices may be utilized to join biological tissues,and more particularly, joining tubular organs to create a fluid channel.The connections between the tubular organs or vessels may be made sideto side, end to end and/or end to side. Typically, there is a graftvessel and a target vessel. The target vessel may be an artery, vein orany other conduit or fluid carrying vessel, for example, coronaryarteries. The graft vessel may comprise a synthetic material, anautologus vessel, a homologus vessel or a xenograft. Anastomosis devicesmay comprise any suitable biocompatible materials, for example, metals,polymers and elastomers. In addition, there are a wide variety ofdesigns and configurations for anastomosis devices depending on the typeof connection to be made. Similarly to stents, anastomosis devices causesome injury to the target vessel, thereby provoking a response from thebody. Therefore, as in the case with stents, there is the potential forsmooth muscle cell proliferation which can lead to blocked connections.Accordingly, there is a need to minimize or substantially eliminatesmooth muscle cell proliferation and inflammation at the anastomoticsite. Rapamycin and/or other drugs, agents or compounds may be utilizedin a manner analogous to stents as described above. In other words; atleast a portion of the anastomosis device may be coated with rapamycinor other drug, agent or compound.

[0139] FIGS. 10-13 illustrate an exemplary anastomosis device 200 for anend to side anastomosis. The exemplary anastomosis device 200 comprisesa fastening flange 202 and attached staple members 204. As stated above,the anastomosis device may comprise any suitable biocomopatiblematerial. Preferably, the anastomosis device 200 comprises a deformablebiocompatible metal, such as a stainless steel alloy, a titanium alloyor a cobalt alloy. Also as stated above, a surface coating or surfacecoating comprising a drug, agent or compound may be utilized to improvethe biocompatibility or other material characteristics of the device aswell as to reduce or substantially eliminate the body's response to itsplacement therein.

[0140] In the exemplary embodiment, the fastening flange 202 resides onthe interior surface 206 of the target vessel wall 208 when theanastomosis is completed. In order to substantially reduce the risk ofhemolysis, thrombogenesis or foreign body reactions, the total mass ofthe fastening flange 202 is preferably as small as possible to reducethe amount of foreign material within the target vessel lumen 210.

[0141] The fastening flange 202 is in the form of a wire ring with aninternal diameter, which when fully expanded, is slightly greater thanthe outside diameter of the graft vessel wall 214 and of the opening 216made in the target vessel wall 208. Initially, the wire ring of thefastening flange 202 has a rippled wave-like shape to reduce thediameter of the ring so that it will easily fit through the opening 216in the target vessel wall 208. The plurality of staple members 204extend substantially perpendicular from the wire ring in the proximaldirection. In the illustrative exemplary embodiment, there are ninestaple members 204 attached to the wire ring fastening flange 202. Othervariations of the anastomosis device 200 might typically have from fourto twelve staple members 204 depending on the size of the vessels to bejoined and the security of attachment required in the particularapplication. The staple members 204 may be integrally formed with thewire ring fastening flange 202 or the staple members 204 may be attachedto the fastening flange 202 by welding, brazing or any other suitablejoining method. The proximal ends 218 of the staple members 204 aresharpened to easily pierce the target vessel wall 208 and the graftvessel wall 214. Preferably, the proximal ends 218 of the staple members204 have barbs 220 to improve the security of the attachment when theanastomosis device 200 is deployed. The anastomosis device 200 isprepared for use by mounting the device onto the distal end of anapplication instrument 222. The fastening flange 202 is mounted on ananvil 224 attached to the distal end of the elongated shaft 226 of theapplication instrument 222. The staple members 204 are compressed inwardagainst a conical holder 228 attached to the instrument 222 proximal tothe anvil 224. The staple members 204 are secured in this position by acap 230 which is slidably mounted on the elongated shaft 226. The cap230 moves distally to cover the sharpened, barbed proximal ends 218 ofthe staple members 204 and to hold them against the conical holder 228.The application instrument 222 is then inserted through the lumen 232 ofthe graft vessel 214. This may be done by inserting the applicationinstrument 222 through the graft vessel lumen 232 from the proximal tothe distal end of the graft vessel 214, or it may be done by backloadingthe elongated shaft 226 of the application instrument 222 into the graftvessel lumen 232 from the distal end to the proximal end, whichever ismost convenient in the case. The anvil 224 and conical holder 228 on thedistal end of the application instrument 222 with the anastomosis device200 attached is extended through the opening 216 into the lumen 210 ofthe target vessel.

[0142] Next, the distal end 234 of the graft vessel wall 214 is evertedagainst the exterior surface 236 of the target vessel wall 208 with thegraft vessel lumen 232 centered over the opening 216 in the targetvessel wall 208. The cap 230 is withdrawn from the proximal ends 218 ofthe staple members 204, allowing the staple members 204 to springoutward to their expanded position. The application instrument 222 isthen drawn in the proximal direction so that the staple members piercethe target vessel wall 208 surrounding the opening 216 and the everteddistil end 234 of the graft vessel 214.

[0143] The application instrument 222 has an annular staple former 238which surrounds the outside of the graft vessel 214. Slight pressure onthe everted graft vessel wall from the annular staple former 238 duringthe piercing step assists in piercing the staple members 204 through thegraft vessel wall 214. Care should be taken not to apply too muchpressure with the annular staple former 238 at this point in the processbecause the staple members 204 could be prematurely deformed before theyhave fully traversed the vessel walls. If desired, an annular surfacemade of a softer material, such as an elastomer, can be provided on theapplication instrument 222 to back up the vessel walls as the staplemembers 204 pierce through them.

[0144] Once the staple members 204 have fully traversed the targetvessel wall 208 and the graft vessel wall 214, the staple former 238 isbrought down with greater force while supporting the fastening flange202 with the anvil 224. The staple members 204 are deformed outward sothat the sharpened, barbed ends 218 pierce back through the everteddistil end 234 and into the target vessel wall 208 to form a permanentattachment. To complete the anastomosis, the anvil 224 is withdrawnthrough the graft vessel lumen 232. As the anvil 224 passes through thewire ring fastening flange 202, it straightens out the wave-like ripplesso that the wire ring flange 202 assumes its full expanded diameter.Alternately, the wire ring fastening flange 202 may be made of aresilient material so that the flange 202 may be compressed and held ina rippled or folded position until it is released within the targetvessel lumen 210, whereupon it will resume its full expanded diameter.Another alternate construction would be to move the anastomosis deviceof a shape-memory alloy so that the fastening flange may be compressedand inserted through the opening in the target vessel, whereupon itwould be returned to its full expanded diameter by heating the device200 to a temperature above the shape-memory transition temperature.

[0145] In the above-described exemplary embodiment, the staple-members204 and/or the wire ring fastening flange 202 may be coated with any ofthe above-described agents, drugs or compounds such as rapamycin toprevent or substantially reduce smooth muscle wall proliferation.

[0146]FIG. 14 illustrates an alternate exemplary embodiment of ananastomosis device. FIG. 14 is a side view of an apparatus for joiningat least two anatomical structures, according to another exemplaryembodiment of the present invention. Apparatus 300 includes a suture 302having a first end 304 and a second end 306, the suture 302 beingconstructed for passage through anatomical structures in a manner to bedescribed subsequently. Suture 302 may be formed from a wide variety ofmaterials, for example, monofilament materials having minimal memory,including polypropylene or polyamide. Any appropriate diameter size maybe used, for example, through 8-0. Other suture types and sizes are alsopossible, of course, and are equally contemplated by the presentinvention.

[0147] A needle 308 preferably is curved and is disposed at the firstend 304 of the suture 302. A sharp tip 310 of needle 308 enables easypenetration of various anatomical structures and enables the needle 308and the suture 302 to readily pass therethrough. The needle 308 may beattached to the suture 302 in various ways, for example, by swedging,preferably substantially matching the outer diameter of the needle 308and the suture 302 as closely as possible.

[0148] Apparatus 300 also includes a holding device 312 disposed at thesecond end 306 of the suture 302. The holding device 312 includes firstand second limbs 314, 316, according to the illustrated exemplaryembodiment, and preferably is of greater stiffness than the suture 302.The first limb 314 may be connected to suture 302 in a number of ways,for example, by swedging, preferably substantially matching the outsidediameter of the suture 302 and the holding device 312 as closely aspossible. The holding device 312 includes a staple structure comprisinga bendable material that preferably is soft and malleable enough tocrimp and hold its crimped position on the outside of an anastomosis.Such materials may include titanium or stainless steel. The holdingdevice 312 may be referred to as a staple, according to the illustratedembodiment, and the suture 302 and the needle 308 a delivery system forstaple 312.

[0149]FIG. 14 illustrates one of the many possible initialconfigurations of holding device 312, i.e. the configuration the holdingdevice 312 is in upon initial passage through the anatomical structuresand/or at a point in time beforehand. As will be described, the holdingdevice 312 is movable from the initial configuration to a holdingconfiguration, in which holding device 312 holds the anatomicalstructures together. According to the illustrated exemplary embodiments,the holding device 312 assumes the holding configuration when it is bentor crimped, as shown in FIG. 19 (further described below).

[0150] The holding device 312 preferably is substantially V-shaped orsubstantially U-shaped, as illustrated, but may assume a wide variety ofshapes to suit particular surgical situations and/or surgeon preference.For example, one of limbs 314, 316 may be straight and the other curved,or limbs 314, 316 may be collinear. The holding device 312 preferably isas smooth and round in cross-section as the needle 308. Further, thediameters of the needle 308, the suture 302, and the holding device 312preferably are substantially identical, especially the needle 308 andthe holding device 312, to avoid creating holes in the anatomicalstructures that are larger than the diameter of the staple 312. Suchholes likely would cause bleeding and/or leakage.

[0151] A method of using apparatus 300 is illustrated in FIGS. 15-19.First, as illustrated in FIG. 15, the needle 308 passes throughanatomical structures 318, 320, which are, for example, vascularstructures. Specifically, according to the illustrated exemplaryembodiment, the needle 308 passes through the edges 322, 324 of vascularstructures 318, 320. Then, as shown in FIG. 16, the needle 308 pullssuture 302 into and through both structures 318, 320. The staple 312then is pulled into desired proximity with structures 318, 320, as shownin FIGS. 17-19, such that it is engaged on both sides of the illustratedanastomosis and associated lumen 326. According to one exemplaryembodiment, traction is placed on suture 302 to hook staple 312 intoposition.

[0152] As illustrated in FIG. 19 and as referenced earlier, the staple312 then is moved from its initial configuration to a holding or crimpedconfiguration 328, in which anatomical structures 318, 320 are joinedtogether to effect an anastomosis between them. The staple 312 creates asubstantially three hundred sixty-degree loop at the edge of theanastomosis, with crimped portion 330 outside lumen 321. A wide varietyof tools and/or mechanisms may be used to crimp the staple 312 into itsholding configuration, for example, in the manner of closure of avascular clip. The same tool, or an alternative tool, may then be usedto separate the staple 312 from the suture 302, for example, by cutting.

[0153] Thus, the staple 312 holds vascular structures 318, 320 togetherfrom inside the vascular structures, as well as from outside, unlike themany prior art staples that secure opposed structures only externally.This achieves a number of advantages, as described above. Not only doesa better approximation result, but crimping a staple is simpler thantying one or more knots and is also less likely traumatic on tissue.Staple closure with a single crimp provides less tension on ananastomosis, for example, than a knot requiring several throws.Embodiments of the invention are especially advantageous in minimallyinvasive surgical situations, as knot-tying with, for example, a knotpusher in a minimally invasive setting through a small port isparticularly tedious and can require up to four or five throws toprevent slippage. Crimping a staple through the port, as withembodiments of the invention, is far simpler and eliminates much of thedifficulty.

[0154] According to one exemplary embodiment, the surgeon achieves aprecise approximation of the vascular or other structures withpreferably a limited number of staples or other holding devices, andthen completes the anastomosis with biologic glue or laser techniques.The holding devices, for example, two or more in number, may be used toorient or line up the structures initially and thus used as a “pilot”for guiding the completion of the anastomosis.

[0155] In the above described exemplary embodiment, the holding device312 may be coated with any of the above-described drugs, agents orcompounds such as rapamycin to prevent or substantially reduce smoothmuscle cell proliferation.

[0156] As described above, various drugs, agents or compounds may belocally delivered via medical devices. For example, rapamycin andheparin may be delivered by a stent to reduce restenosis, inflammation,and coagulation. Various techniques for immobilizing the drugs, agentsor compounds are discussed above, however, maintaining the drugs, agentsor compounds on the medical devices during delivery and positioning iscritical to the success of the procedure or treatment. For example,removal of the drug, agent or compound coating during delivery of thestent can potentially cause failure of the device. For a self-expandingstent, the retraction of the restraining sheath may cause the drugs,agents or compounds to rub off the stent. For a balloon expandablestent, the expansion of the balloon may cause the drugs, agents orcompounds to simply delaminate from the stent through contact with theballoon or via expansion. Therefore, prevention of this potentialproblem is important to have a successful therapeutic medical device,such as a stent.

[0157] There are a number of approaches that may be utilized tosubstantially reduce the above-described concern. In one exemplaryembodiment, a lubricant or mold release agent may be utilized. Thelubricant or mold release agent may comprise any suitable biocompatiblelubricious coating. An exemplary lubricious coating may comprisesilicone. In this exemplary embodiment, a solution of the silicone basecoating may be introduced onto the balloon surface, onto the polymericmatrix, and/or onto the inner surface of the sheath of a self-expandingstent delivery apparatus and allowed to air cure. Alternately, thesilicone based coating may be incorporated into the polymeric matrix. Itis important to note, however, that any number of lubricious materialsmay be utilized, with the basic requirements being that the material bebiocompatible, that the material not interfere with theactions/effectiveness of the drugs, agents or compounds and that thematerial not interfere with the materials utilized to immobilize thedrugs, agents or compounds on the medical device. It is also importantto note that one or more, or all of the above-described approaches maybe utilized in combination.

[0158] Referring now to FIG. 20, there is illustrated a balloon 400 of aballoon catheter that may be utilized to expand a stent in situ. Asillustrated, the balloon 400 comprises a lubricious coating 402. Thelubricious coating 402 functions to minimize or substantially eliminatethe adhesion between the balloon 400 and the coating on the medicaldevice. In the exemplary embodiment described above, the lubriciouscoating 402 would minimize or substantially eliminate the adhesionbetween the balloon 400 and the heparin or rapamycin coating. Thelubricious coating 402 may be attached to and maintained on the balloon400 in any number of ways including but not limited to dipping,spraying, brushing or spin coating of the coating material from asolution or suspension followed by curing or solvent removal step asneeded.

[0159] Materials such as synthetic waxes, e.g. diethyleneglycolmonostearate, hydrogenated castor oil, oleic acid, stearic acid, zincstearate, calcium stearate, ethylenebis (stearamide), natural productssuch as paraffin wax, spermaceti wax, carnuba wax, sodium alginate,ascorbic acid and flour, fluorinated compounds such as perfluoroalkanes,perfluorofatty acids and alcohol, synthetic polymers such as siliconese.g. polydimethylsiloxane, polytetrafluoroethylene, polyfluoroethers,polyalkylglycol e.g. polyethylene glycol waxes, and inorganic materialssuch as talc, kaolin, mica, and silica may be used to prepare thesecoatings. Vapor deposition polymerization e.g. parylene-C deposition, orRF-plasma polymerization of perfluoroalkenes and perfluoroalkanes canalso be used to prepare these lubricious coatings.

[0160]FIG. 21 illustrates a cross-section of a band 102 of the stent 100illustrated in FIG. 1. In this exemplary embodiment, the lubriciouscoating 500 is immobilized onto the outer surface of the polymericcoating. As described above, the drugs, agents or compounds may beincorporated into a polymeric matrix. The stent band 102 illustrated inFIG. 21 comprises a base coat 502 comprising a polymer and rapamycin anda top coat 504 or diffusion layer 504 also comprising a polymer. Thelubricious coating 500 is affixed to the top coat 502 by any suitablemeans, including but not limited to spraying, brushing, dipping or spincoating of the coating material from a solution or suspension with orwithout the polymers used to create the top coat, followed by curing orsolvent removal step as needed. Vapor deposition polymerization andRF-plasma polymerization may also be used to affix those lubriciouscoating materials that lend themselves to this deposition method, to thetop coating. In an alternate exemplary embodiment, the lubriciouscoating may be directly incorporated into the polymeric matrix.

[0161] If a self-expanding stent is utilized, the lubricious coating maybe affixed to the inner surface of the restraining sheath. FIG. 22illustrates a partial cross-sectional view of self-expanding stent 200within the lumen of a delivery apparatus sheath 14. As illustrated, alubricious coating 600 is affixed to the inner surfaces of the sheath14. Accordingly, upon deployment of the stent 200, the lubriciouscoating 600 preferably minimizes or substantially eliminates theadhesion between the sheath 14 and the drug, agent or compound coatedstent 200.

[0162] In an alternate approach, physical and/or chemical cross-linkingmethods may be applied to improve the bond strength between thepolymeric coating containing the drugs, agents or compounds and thesurface of the medical device or between the polymeric coatingcontaining the drugs, agents or compounds and a primer. Alternately,other primers applied by either traditional coating methods such as dip,spray or spin coating, or by RF-plasma polymerization may also be usedto improve bond strength. For example, as shown in FIG. 23, the bondstrength can be improved by first depositing a primer layer 700 such asvapor polymerized parylene-C on the device surface, and then placing asecondary layer 702 which comprises a polymer that is similar inchemical composition to the one or more of the polymers that make up thedrug-containing matrix 704, e.g., polyethylene-co-vinyl acetate orpolybutyl methacrylate but has been modified to contain cross-linkingmoieties. This secondary layer 702 is then cross-linked to the primerafter exposure to ultra-violet light. It should be noted that anyonefamiliar with the art would recognize that a similar outcome could beachieved using cross-linking agents that are activated by heat with orwithout the presence of an activating agent. The drug-containing matrix704 is then layered onto the secondary layer 702 using a solvent thatswells, in part or wholly, the secondary layer 702. This promotes theentrainment of polymer chains from the matrix into the secondary layer702 and conversely from the secondary layer 702 into the drug-containingmatrix 704. Upon removal of the solvent from the coated layers, aninterpenetrating or interlocking network of the polymer chains is formedbetween the layers thereby increasing the adhesion strength betweenthem. A top coat 706 is used as described above.

[0163] A related difficulty occurs in medical devices such as stents. Inthe drug-coated stents crimped state, some struts come into contact witheach other and when the stent is expanded, the motion causes thepolymeric coating comprising the drugs, agents or compounds to stick andstretch. This action may potentially cause the coating to separate fromthe stent in certain areas. The predominant mechanism of the coatingself-adhesion is believed to be due to mechanical forces. When thepolymer comes in contact with itself, its chains can tangle causing themechanical bond, similar to Velcro®. Certain polymers do not bond witheach other, for example, fluoropolymers. For other polymers, however,powders may be utilized. In other words, a powder may be applied to theone or more polymers incorporating the drugs, agents or other compoundson the surfaces of the medical device to reduce the mechanical bond. Anysuitable biocompatible material which does not interfere with the drugs,agents, compounds or materials utilized to immobilize the drugs, agentsor compounds onto the medical device may be utilized. For example, adusting with a water soluble powder may reduce the tackiness of thecoatings surface and this will prevent the polymer from sticking toitself thereby reducing the potential for delamination. The powdershould be water-soluble so that it does not present an emboli risk. Thepowder may comprise an anti-oxidant, such as vitamin C, or it maycomprise an anti-coagulant, such as aspirin or heparin. An advantage ofutilizing an anti-oxidant may be in the fact that the anti-oxidant maypreserve the other drugs, agents or compounds over longer periods oftime.

[0164] It is important to note that crystalline polymers are generallynot sticky or tacky. Accordingly, if crystalline polymers are utilizedrather than amorphous polymers, then additional materials may not benecessary. It is also important to note that polymeric coatings withoutdrugs, agents and/or compounds may improve the operating characteristicsof the medical device. For example, the mechanical properties of themedical device may be improved by a polymeric coating, with or withoutdrugs, agents and/or compounds. A coated stent may have improvedflexibility and increased durability. In addition, the polymeric coatingmay substantially reduce or eliminate galvanic corrosion between thedifferent metals comprising the medical device. The same holds true foranastomosis devices.

[0165] Any of the above-described medical devices may be utilized forthe local delivery of drugs, agents and/or compounds to other areas, notimmediately around the device itself. In order to avoid the potentialcomplications associated with systemic drug delivery, the medicaldevices of the present invention may be utilized to deliver therapeuticagents to areas adjacent to the medical device. For example, a rapamycincoated stent may deliver the rapamycin to the tissues surrounding thestent as well as areas upstream of the stent and downstream of thestent. The degree of tissue penetration depends on a number of factors,including the drug, agent or compound, the concentrations of the drugand the release rate of the agent. The same holds true for coatedanastomosis devices.

[0166] The drug, agent and/or compound/carrier or vehicle compositionsdescribed above may be formulated in a number of ways. For example, theymay be formulated utilizing additional components or constituents,including a variety of excipient agents and/or formulary components toaffect manufacturability, coating integrity, sterilizability, drugstability, and drug release rate. Within exemplary embodiments of thepresent invention, excipient agents and/or formulary components may beadded to achieve both fast-release and sustained-release drug elutionprofiles. Such excipient agents may include salts and/or inorganiccompounds such as acids/bases or buffer components, anti-oxidants,surfactants, polypeptides, proteins, carbohydrates including sucrose,glucose or dextrose, chelating agents such as EDTA, glutathione or otherexcipients or agents.

[0167] It is important to note that any of the above-described medicaldevices may be coated with coatings that comprise drugs, agents orcompounds or simply with coatings that contain no drugs, agents orcompounds. In addition, the entire medical device may be coated or onlya portion of the device may be coated. The coating may be uniform ornon-uniform. The coating may be discontinuous.

[0168] As described above, any number of drugs, agents and/or compoundsmay be locally delivered via any number of medical devices. For example,stents and anastomosis devices may incorporate coatings comprisingdrugs, agents and/or compounds to treat various disease states andreactions by the body as described in detail above. Other devices whichmay be coated with or otherwise incorporate therapeutic dosages ofdrugs, agents and/or compounds include stent-grafts, which are brieflydescribed above, and devices utilizing stent-grafts, such as devices fortreating abdominal aortic aneurysms as well as other aneurysms, e.g.thoracic aorta aneurysms.

[0169] Stent-grafts, as the name implies, comprise a stent and a graftmaterial attached thereto. FIG. 24 illustrates an exemplary stent-graft800. The stent-graft 800 may comprise any type of stent and any type ofgraft material as described in detail subsequently. In the illustratedexemplary embodiment, the stent 802 is a self-expanding device. Atypical self-expanding stent comprises an expandable lattice or networkof interconnected struts. In preferred embodiments of the invention, thelattice is fabricated, e.g. laser cut, from an integral tube ofmaterial.

[0170] In accordance with the present invention, the stent may bevariously configured. For example, the stent may be configured withstruts or the like that form repeating geometric shapes. One skilled inthe art will readily recognize that a stent may be configured or adaptedto include certain features and/or to perform a certain function(s), andthat alternate designs may be used to promote that feature or function.

[0171] In the exemplary embodiment of the invention illustrated in FIG.24, the matrix or struts of stent 802 may be configured into at leasttwo hoops 804, each hoop 804 comprising a number of struts 806 formedinto a diamond shape, having approximately nine diamonds. The stent 802may further include a zigzag shaped ring 808 for connecting adjacenthoops to one another. The zigzag shaped rings 808 may be formed from anumber of alternating struts 810, wherein each ring has fifty-fourstruts.

[0172] An inner or outer surface of the stent 802 may be covered by orsupport a graft material. Graft material 812 may be made from any numberof materials known to those skilled in the art, including woven or otherconfigurations of polyester, Dacron®, Teflon®, polyurethane porouspolyurethane, silicone, polyethylene, terephthalate, expandedpolytetrafluoroethylene (ePTFE) and blends of various materials.

[0173] The graft material 812 may be variously configured, preferably toachieve predetermined mechanical properties. For example, the graftmaterial may incorporate a single or multiple weaving and/or pleatingpatterns, or may be pleated or unpleated. For example, the graftmaterial may be configured into a plain weave, a satin weave, includelongitudinal pleats, interrupted pleats, annular or helical pleats,radially oriented pleats, or combinations thereof. Alternately, thegraft material may be knitted or braided. In the embodiments of theinvention in which the graft material is pleated, the pleats may becontinuous or discontinuous. Also, the pleats may be orientedlongitudinally, circumferentially, or combinations thereof., Asillustrated in FIG. 24, the graft material 812 may include a pluralityof longitudinal pleats 814 extending along its surface, generallyparallel to the longitudinal axis of the stent-graft 800. The pleats 814allow the stent-graft 800 to collapse around its center, much as itwould be when it is delivered into a patient. This provides a relativelylow profile delivery system, and provides for a controlled andconsistent deployment therefrom. It is believed that this configurationminimizes wrinkling and other geometric irregularities. Upon subsequentexpansion, the stent-graft 800 assumes its natural cylindrical shape,and the pleats 814 uniformly and symmetrically open.

[0174] In addition, the pleats 814 help facilitate stent-graftmanufacture, in that they indicate the direction parallel to thelongitudinal axis, allowing stent to graft attachment along these lines,and thereby inhibiting accidental twisting of the graft relative to thestent after attachment. The force required to push the stent-graft 800out of the delivery system may also be reduced, in that only the pleatededges of the graft make frictional contact with the inner surface of thedelivery system. One further advantage of the pleats 814 is that bloodtends to coagulate generally uniformly in the troughs of the pleats 814,discouraging asymmetric or large clot formation on the graft surface,thereby reducing embolus risk.

[0175] As shown in FIG. 24, the graft material 812 may also include oneor more, and preferably a plurality of, radially oriented pleatinterruptions 816. The pleat interruptions 816 are typicallysubstantially circular and are oriented perpendicular to longitudinalaxis. Pleat interruptions 816 allow the graft and stent to bend betterat selective points. This design provides for a graft material that hasgood crimpability and improved kink resistance.

[0176] The foregoing graft materials may be braided, knitted or woven,and may be warp or weft knitted. If the material is warp knitted, it maybe provided with a velour, or towel like surface; which is believed tospeed the formation of blood clots, thereby promoting the integration ofa stent-graft or stent-graft component into the surrounding cellularstructure.

[0177] A graft material may be attached to a stent or to another graftmaterial by any number of structures or methods known to those skilledin the art, including adhesives, such as polyurethane glue; a pluralityof conventional sutures of polyvinylidene fluoride, polypropylene,Dacron®, or any other suitable material; ultrasonic welding; mechanicalinterference fit; and staples.

[0178] The stent 802 and/or graft material 812 may be coated with any ofthe above-described drugs, agents and/or compounds. In one exemplaryembodiment, rapamycin may be affixed to at least a portion of the graftmaterial 812 utilizing any of the materials and processes describedabove. In another exemplary embodiment, rapamycin may be affixed to atleast a portion of the graft material 812 and heparin or otherantithrombotics may be affixed to at least a portion of the stent 802.With this configuration, the rapamycin coated graft material 812 may beutilized to minimize or substantially eliminate smooth muscle cellhyperproliferation and the heparin coated stent may substantially reducethe chance of thrombosis.

[0179] The particular polymer(s) utilized depends on the particularmaterial upon which it is affixed. In addition, the particular drug,agent and/or compound may also affect the selection of polymer(s). Asset forth above, rapamycin may be affixed to at least a portion of thegraft material 812 utilizing the polymer(s) and processes describedabove. In another alternate exemplary embodiment, the rapamycin or anyother drug, agent and/or compound may be directly impregnated into thegraft material 812 utilizing any number of known techniques.

[0180] In yet another alternate exemplary embodiment, the stent-graftmay be formed from two stents with the graft material sandwichedtherebetween. FIG. 25 is a simple illustration of a stent-graft 900formed from an inner stent 902, an outer stent 904 and graft material906 sandwiched therebetween. The stents 902, 904 and graft material 906may be formed from the same materials as described above. As before, theinner stent 902 may be coated with an antithrombotic or anticoagulantsuch as heparin while the outer stent 904 may be coated with anantiproliferative such as rapamycin. Alternately, the graft material 906may be coated with any of the above described drugs, agents and/orcompounds, as well as combinations thereof, or all three elements may becoated with the same or different drugs, agents and/or compounds.

[0181] In yet another alternate exemplary embodiment, the stent-graftdesign may be modified to include a graft cuff. As illustrated in FIG.26, the graft material 906 may be folded around the outer stent 904 toform cuffs 908. In this exemplary embodiment, the cuffs 908 may beloaded with various drugs, agents and/or compounds, including rapamycinand heparin. The drugs, agents and/or compounds may be affixed to thecuffs 908 utilizing the methods and materials described above or throughother means. For example, the drugs, agents and/or compounds may betrapped in the cuffs 908 with the graft material 906 acting as thediffusion barrier through which the drug, agent and/or compound elutes.The particular material selected as well as its physical characteristicswould determine the elution rate. Alternately, the graft material 906forming the cuffs 908 may be coated with one or more polymers to controlthe elution rate as described above.

[0182] Stent-grafts may be utilized to treat aneurysms. An aneurysm isan abnormal dilation of a layer or layers of an arterial wall, usuallycaused by a systemic collagen synthetic or structural defect. Anabdominal aortic aneurysm is an aneurysm in the abdominal portion of theaorta, usually located in or near one or both of the two iliac arteriesor near the renal arteries. The aneurysm often arises in the infrarenalportion of the diseased aorta, for example, below the kidneys. Athoracic aortic aneurysm is an aneurysm in the thoracic portion of theaorta. When left untreated, the aneurysm may rupture, usually causingrapid fatal hemorrhaging.

[0183] Aneurysms may be classified or typed by their position as well asby the number of aneurysms in a cluster. Typically, abdominal aorticaneurysms may be classified into five types. A Type I aneurysm is asingle dilation located between the renal arteries and the iliacarteries. Typically, in a Type 1 aneurysm, the aorta is healthy betweenthe renal arteries and the aneurysm and between the aneurysm and theiliac arteries.

[0184] A Type II A aneurysm is a single dilation located between therenal arteries and the iliac arteries. In a Type II A aneurysm, theaorta is healthy between the renal arteries and the aneurysm, but nothealthy between the aneurysm and the iliac arteries. In other words, thedilation extends to the aortic bifurcation. A Type II B aneurysmcomprises three dilations. One dilation is located between the renalarteries and the iliac arteries. Like a Type II A aneurysm, the aorta ishealthy between the aneurysm and the renal arteries, but not healthybetween the aneurysm and the iliac arteries. The other two dilations arelocated in the iliac arteries between the aortic bifurcation and thebifurcations between the external iliacs and the internal iliacs. Theiliac arteries are healthy between the iliac bifurcation and theaneurysms. A Type II C aneurysm also comprises three dilations. However,in a Type II C aneurysm, the dilations in the iliac arteries extend tothe iliac bifurcation.

[0185] A Type III aneurysm is a single dilation located between therenal arteries and the iliac arteries. In a Type III aneurysm, the aortais not healthy between the renal arteries and the aneurysm. In otherwords, the dilation extends to the renal arteries.

[0186] A ruptured abdominal aortic aneurysm is presently the thirteenthleading cause of death in the United States. The routine management ofabdominal aortic aneurysms has been surgical bypass, with the placementof a graft in the involved or dilated segment. Although resection with asynthetic graft via transperitoneal or retroperitoneal approach has beenthe standard treatment, it is associated with significant risk. Forexample, complications include perioperative myocardial ischemia, renalfailure, erectile impotence, intestinal ischemia, infection, lower limbischemia, spinal cord injury with paralysis, aorta-enteric fistula, anddeath. Surgical treatment of abdominal aortic aneurysms is associatedwith an overall mortality rate of five percent in asymptomatic patients,sixteen to nineteen percent in symptomatic patients, and is as high asfifty percent in patients with ruptured abdominal aortic aneurysms.

[0187] Disadvantages associated with conventional surgery, in additionto the high mortality rate, include an extended recovery periodassociated with the large surgical incision and the opening of theabdominal cavity, difficulties in suturing the graft to the aorta, theloss of the existing thrombosis to support and reinforce the graft, theunsuitability of the surgery for many patients having abdominal aorticaneurysms, and the problems associated with performing the surgery on anemergency basis after the aneurysm has ruptured. Further, the typicalrecovery period is from one to two weeks in the hospital, and aconvalescence period at home from two to three months or more, ifcomplications ensue. Since many patients having abdominal aorticaneurysms have other chronic illnesses, such as heart, lung, liverand/or kidney disease, coupled with the fact that many of these patientsare older, they are less than ideal candidates for surgery.

[0188] The occurrence of aneurysms is not confined to the abdominalregion. While abdominal aortic aneurysms are generally the most common,aneurysms in other regions of the aorta or one of its branches arepossible. For example, aneurysms may occur in the thoracic aorta. As isthe case with abdominal aortic aneurysms, the widely accepted approachto treating an aneurysm in the thoracic aorta is surgical repair,involving replacing the aneurysmal segment with a prosthetic device.This surgery, as described above, is a major undertaking, withassociated high risks and with significant mortality and morbidity.

[0189] Over the past five years, there has been a great deal of researchdirected at developing less invasive, percutaneous, e.g., catheterdirected, techniques for the treatment of aneurysms, specificallyabdominal aortic aneurysms. This has been facilitated by the developmentof vascular stents, which can and have been used in conjunction withstandard or thin-wall graft material in order to create a stent-graft orendograft. The potential advantages of less invasive treatments haveincluded reduced surgical morbidity and mortality along with shorterhospital and intensive care unit stays.

[0190] Stent-grafts or endoprostheses are now FDA approved andcommercially available. The delivery procedure typically involvesadvanced angiographic techniques performed through vascular accessesgained via surgical cutdown of a remote artery, such as the commonfemoral or brachial arteries. Over a guidewire, the appropriate sizeintroducer will be placed. The catheter and guidewire are passed throughthe aneurysm, and, with the appropriate size introducer housing astent-graft, the stent-graft will be advanced along the guidewire to theappropriate position. Typical deployment of the stent-graft devicerequires withdrawal of an outer sheath while maintaining the position ofthe stent-graft with an inner-stabilizing device. Most stent-grafts areself-expanding; however, an additional angioplasty procedure, e.g.,balloon angioplasty, may be required to secure the position of thestent-graft. Following the placement of the stent-graft, standardangiographic views may be obtained.

[0191] Due to the large diameter of the above-described devices,typically greater than twenty French (3F=1 mm), arteriotomy closurerequires surgical repair. Some procedures may require additionalsurgical techniques, such as hypogastric artery embolization, vesselligation, or surgical bypass, in order to adequately treat the aneurysmor to maintain flow to both lower extremities. Likewise, some procedureswill require additional, advanced catheter directed techniques, such asangioplasty, stent placement, and embolization, in order to successfullyexclude the aneurysm and efficiently manage leaks.

[0192] While the above-described endoprostheses represent a significantimprovement over conventional surgical techniques, there is a need toimprove the endoprostheses, their method of use and their applicabilityto varied biological conditions. Accordingly, in order to provide a safeand effective alternate means for treating aneurysms, includingabdominal aortic aneurysms and thoracic aortic aneurysms, a number ofdifficulties associated with currently known endoprostheses and theirdelivery systems must be overcome. One concern with the use ofendoprostheses is the prevention of endo-leaks and the disruption of thenormal fluid dynamics of the vasculature. Devices using any technologyshould preferably be simple to position and reposition as necessary,should preferably provide an acute fluid tight seal, and shouldpreferably be anchored to prevent migration without interfering withnormal blood flow in both the aneurysmal vessel as well as branchingvessels. In addition, devices using the technology should preferably beable to be anchored, sealed, and maintained in bifurcated vessels,tortuous vessels, highly angulated vessels, partially diseased vessels,calcified vessels, odd shaped vessels, short vessels, and long vessels.In order to accomplish this, the endoprostheses should preferably beextendable and re-configurable while maintaining acute and long termfluid tight seals and anchoring positions.

[0193] The endoprostheses should also preferably be able to be deliveredpercutaneously utilizing catheters, guidewires and other devices whichsubstantially eliminate the need for open surgical intervention.Accordingly, the diameter of the endoprostheses in the catheter is animportant factor. This is especially true for aneurysms in the largervessels, such as the thoracic aorta.

[0194] As stated above, one or more stent-grafts may be utilized totreat aneurysms. These stent-grafts or endoprostheses may comprise anynumber of materials and configurations. FIG. 27 illustrates an exemplarysystem for treating abdominal aortic aneurysms. The system 1000 includesa first prosthesis 1002 and two second prostheses 1004 and 1006, whichin combination, bypass an aneurysm 1008. In the illustrated exemplaryembodiment, a proximal portion of the system 1000 may be positioned in asection 1010 of an artery upstream of the aneurysm 1008, and a distalportion of the system 1000 may be positioned in a downstream section ofthe artery or a different artery such as iliacs 1012 and 1014.

[0195] A prosthesis used in a system in accordance with the presentinvention typically includes a support, stent or lattice ofinterconnected struts defining an interior space or lumen having an openproximal end and an open distal end. The lattice also defines aninterior surface and an exterior surface. The interior and/or exteriorsurfaces of the lattice, or a portion of the lattice, may be covered byor support at least one gasket material or graft material.

[0196] In preferred embodiments of the invention, a prosthesis ismoveable between an expanded or inflated position and an unexpanded ordeflated position, and any position therebetween. In some exemplaryembodiments of the invention, it may be desirable to provide aprosthesis that moves only from fully collapsed to fully expanded. Inother exemplary embodiments of the invention, it may be desirable toexpand the prosthesis, then collapse or partially collapse theprosthesis. Such capability is beneficial to the surgeon to properlyposition or re-position the prosthesis. In accordance with the presentinvention, the prosthesis may be self-expanding, or may be expandableusing an inflatable device, such as a balloon or the like.

[0197] Referring back to FIG. 27, the system 1000 is deployed in theinfrarenal neck 1010 of the abdominal aorta, upstream of where theartery splits into first and second common iliac arteries 1012, 1014.FIG. 27 shows the first prosthesis or stent gasket 1002 positioned inthe infrarenal neck 1010; two second prostheses, 1004, 1006, theproximal ends of which matingly engage a proximal portion of stentgasket 1002, and the distal ends of which extend into a common iliacartery 1012 or 1014. As illustrated, the body of each second prosthesisforms a conduit or fluid flow path that passes through the location ofthe aneurysm 1008. In preferred embodiments of the invention, thecomponents of the system 1000 define a fluid flow path that bypasses thesection of the artery where the aneurysm is located.

[0198] The first prosthesis includes a support matrix or stent thatsupports a sealing material or foam, at least a portion of which ispositioned across a biological fluid flow path, e.g., across a bloodflow path. In preferred embodiments of the invention, the firstprosthesis, the stent, and the sealing material are radially expandable,and define a hollow space between a proximal portion of the prosthesisand a distal portion of the prosthesis. The first prosthesis may alsoinclude one or more structures for positioning and anchoring theprosthesis in the artery, and one or more structures for engaging andfixing at least one second prosthesis in place, e.g., a bypassprosthesis.

[0199] The support matrix or stent of the first prosthesis may be formedof a wide variety of materials, may be configured in a wide variety ofshapes, and their shapes and uses are well known in the art. Exemplaryprior art stents are disclosed in U.S. Pat. No. 4,733,665 (Palmaz); U.S.Pat. No. 4,739,762 (Palmaz); and U.S. Pat. No. 4,776,337 (Palmaz), eachof the foregoing patents being incorporated herein by reference.

[0200] In preferred embodiments of the invention, the stent of the firstprosthesis is a collapsible, flexible, and self-expanding lattice ormatrix formed from a metal or metal alloy, such as nitinol or stainlesssteel. Structures formed from stainless steel may be made self-expandingby configuring the stainless steel in a predetermined manner, forexample, by twisting it into a braided configuration. More preferably,the stent is a tubular frame that supports a sealing material. The termtubular, as used herein, refers to any shape having a sidewall orsidewalls defining a hollow space or lumen extending therebetween; thecross-sectional shape may be generally cylindrical, elliptic, oval,rectangular, triangular, or any other shape. Furthermore, the shape maychange or be deformable as a consequence of various forces that maypress against the stent or prosthesis.

[0201] The sealing material or gasket member supported by the stent maybe formed of a wide variety of materials, may be configured in a widevariety of shapes, and their shapes and uses are well known in the art.Exemplary materials for use with this aspect of the invention aredisclosed in U.S. Pat. No. 4,739,762 (Palmaz) and U.S. Pat. No.4,776,337 (Palmaz), both incorporated herein by reference.

[0202] The sealing material or gasket member may comprise any suitablematerial. Exemplary materials preferably comprise a biodurable andbiocompatible material, including but are not limited to, open cell foammaterials and closed cell foam materials. Exemplary materials includepolyurethane, polyethylene, polytetrafluoroethylene; and other variouspolymer materials, preferably woven or knitted, that provide a flexiblestructure, such as Dacron®. Highly compressible foams are particularlypreferred, preferably to keep the crimped profile low for betterdelivery. The sealing material or foam is preferably substantiallyimpervious to blood when in a compressed state.

[0203] The sealing material may cover one or more surfaces of the stenti.e., may be located along an interior or exterior wall, or both, andpreferably extends across the proximal end or a proximal portion of thestent. The sealing material helps impede any blood trying to flow aroundthe first prosthesis, e.g., between the first prosthesis and thearterial wall, and around one or more bypass prostheses after they havebeen deployed within the lumen of the first prosthesis (described inmore detail below).

[0204] In preferred embodiments of the invention, the sealing materialstretches or covers a portion of the proximal end of the stent and alongat least a portion of the outside wall of the stent.

[0205] In some embodiments of the invention, it may be desirable for theportion of the sealing material covering the proximal portion of thestent to include one or more holes, apertures, points, slits, sleeves,flaps, weakened spots, guides, or the like for positioning a guidewire,for positioning a system component, such as a second prosthesis, and/orfor engaging, preferably matingly engaging, one or more systemcomponents, such as a second prosthesis. For example, a sealing materialconfigured as a cover or the like, and having a hole, may partiallyocclude the stent lumen.

[0206] These openings may be variously configured, primarily to conformto its use. These structures promote proper side by side placement ofone or more, preferably multiple, prostheses within the firstprosthesis, and, in some embodiments of the invention, the sealingmaterial may be configured or adapted to assist in maintaining a certainshape of the fully deployed system or component. Further, these openingsmay exist prior to deployment of the prosthesis, or may be formed in theprosthesis as part of a deployment procedure. The various functions ofthe openings will be evident from the description below. In exemplaryembodiments of the invention, the sealing material is a foam cover thathas a single hole.

[0207] The sealing material may be attached to the stent by any of avariety of connectors, including a plurality of conventional sutures ofpolyvinylidene fluoride, polypropylene, Dacron®, or any other suitablematerial and attached thereto. Other methods of attaching the sealingmaterial to the stent include adhesives, ultrasonic welding, mechanicalinterference fit and staples.

[0208] One or more markers may be optionally disposed in or on the stentbetween the proximal end and the distal end. Preferably, two or moremarkers are sized and/or positioned to identify a location on theprosthesis, or to identify the position of the prosthesis, or a portionthereof, in relation to an anatomical feature or another systemcomponent.

[0209] First prosthesis is typically deployed in an arterial passagewayupstream of an aneurysm, and functions to open and/or expand the artery,to properly position and anchor the various components of the system,and, in combination with other components, seal the system or portionsthereof from fluid leaks. For example, the sealing prosthesis may bedeployed within the infrarenal neck, between an abdominal aorticaneurysm and the renal arteries of a patient, to assist in repairing anabdominal aortic aneurysm.

[0210] FIGS. 27-29 show an exemplary sealing prosthesis of the presentinvention. Sealing prosthesis 1002 includes a cylindrical or ovalself-expanding lattice, support, or stent 1016, typically made from aplurality of interconnected struts 1018. Stent 1016 defines an interiorspace or lumen 1020 having two open ends, a proximal end 1022 and adistal end 1024. One or more markers 1026 may be optionally disposed inor on the stent between the proximal end 1022 and the distal end 1024.

[0211] Stent 1016 may further include at least two but preferably eight(as shown in FIG. 28) spaced apart longitudinal legs 1028. Preferably,there is a leg extending from each apex 1030 of diamonds formed bystruts 1018. At least one leg, but preferably each leg, includes aflange 1032 adjacent its distal end which allows for the stent 1016 tobe retrievable into its delivery apparatus after partial or nearly fulldeployment thereof so that it can be turned, or otherwise repositionedfor proper alignment.

[0212]FIG. 29 shows the sealing material 1034 covering the proximal end1022 of stent gasket 1002. In the exemplary embodiment shown in FIG. 29,sealing prosthesis 1002 includes a sealing material 1034 having a firstopening or hole 1036 and a second opening or slit 1038. The gasketmaterial covers at least a portion of the interior or exterior of thestent, and most preferably covers substantially all of the exterior ofthe stent. For example, gasket material 1034 may be configured to coverstent 1016 from the proximal end 1022 to the distal end 1024, butpreferably not covering longitudinal legs 1028.

[0213] The sealing material 1034 helps impede any blood trying to flowaround bypass prostheses 1004 and 1006 after they have been deployed (asshown in FIG. 27) and from flowing around the stent gasket 1002 itself.For this embodiment, sealing material 1034 is a compressible member orgasket located along the exterior of the stent 1016 and at least aportion of the interior of the stent 1016.

[0214] The second prostheses 1004 and 1006 may comprise stent-graftssuch as described with respect to FIG. 24 and may be coated with any ofthe drugs, agents and/or compounds as described above. In other words,the stent and/or the graft material may be coated with any of theabove-described drugs, agents and/or compounds utilizing any of theabove-described polymers and processes. The stent gasket 1002 may alsobe coated with any of the above-described drugs, agents and/orcompounds. In other words, the stent and/or sealing material may becoated with any of the above-described drugs, agents and/or compoundsutilizing any of the above-described polymers and processes. Inparticular, rapamycin and heparin may be of importance to prevent smoothmuscle cell hyperproliferation and thrombosis. Other drugs, agentsand/or compounds may be utilized as well. For example drugs, agentsand/or compounds which promote re-endotheliazation may be utilized tofacilitate incorporation of the prosthesis into the living organism.Also, embolic material may be incorporated into the stent-graft toreduce the likelihood of endo leaks.

[0215] It is important to note that the above-described system forrepairing abdominal aortic aneurysms is one example of such a system.Any number of aneurysmal repair systems comprising stent-grafts may becoated with the appropriate drugs, agents and/or compounds, as well ascombinations thereof. For example, thoracic aorta aneurysms may berepaired in a similar manner. Regardless of the type of aneurysm or itsposition within the living organism, the components comprising therepair system may be coated with the appropriate drug, agent and/orcompound as described above with respect to stent-grafts.

[0216] A difficulty associated with the treatment of aneurysms,specifically abdominal aortic aneurysms, is endoleaks. An endoleak isgenerally defined as the persistence of blood flow outside of the lumenof the stent-graft, but within the aneurysmal sac or adjacent vascularsegment being treated with the stent-graft. Essentially, endoleaks arecaused by one of two primary mechanisms, wherein each mechanism has anumber of possible modalities. The first mechanism involves theincomplete sealing or exclusion of the aneurysmal sac or vessel segment.The second mechanism involves retrograde flow. In this type of endoleak,blood-flow into the aneurysmal sac is reversed due to retrograde flowfrom patent collateral vessels, particularly the lumbar arteries or theinferior mesenteric artery. This type of endoleak may occur even when acomplete seal has been achieved around the stent-grafts. It is alsopossible that an endoleak may develop due to stent-graft failure, forexample, a tear in the graft fabric.

[0217] Endoleaks may be classified by type. A type I endoleak is aperigraft leak at the proximal or distal attachment sites of thestent-grafts. Essentially, this type of endoleak occurs when apersistent perigraft channel of blood flow develops due to anineffective or inadequate seal at the ends of the stent-graft. There area number of possible causes of a type I endoleak, including impropersizing of the stent-graft, migration of the stent-graft, incompletestent-graft expansion and an irregular shape of the arterial lumen. Atype II endoleak is persistent collateral blood flow into the aneurysmalsac from a patent branch of the aorta. Essentially, the pressure in theaneurysmal sac is lower than the collateral branches, thereby causing aretrograde blood flow. Sources of type II endoleaks include theaccessory renal arteries, the testicular arteries, the lumbar arteries,the middle sacral artery, the inferior mesenteric artery and the spinalartery. A type III endoleak may be caused by a structural failure of theabdominal aortic aneurysm repair system or its components, for example,the stent-grafts. A type III endoleak may also be caused by a junctionfailure in systems employing modular components. Sources of type IIIendoleaks include tears, rips or holes in the fabric of the stent-graft,improper sizing of the modular components and limited overlap of themodular components. A type IV endoleak is blood flow through the graftmaterial itself. The blood flow through the pores of the graft materialor through small holes in the fabric caused by the staples or suturesattaching the graft material to the stent. Blood flow through the porestypically occurs with highly porous graft fabrics. A type V endoleak orendotension is a persistent or recurrent pressurization of theaneurysmal sac without any radiologically detectable endoleak. Possiblecauses of a type V endoleak include pressure transmission by thrombus,highly porous graft material, or the adjacent aortic lumen.

[0218] There are a number of possible treatment options for each type ofendoleak described above. The particular treatment option depends mainlyupon the cause of endoleak and the options are not always successful.The present invention is directed to a modification of existingendovascular abdominal aortic aneurysm repair systems or devices, suchas the exemplary devices described herein, that is intended to eliminateor substantially reduce the incidence of endoleaks.

[0219] The modification comprises coating at least a portion of thevarious components comprising an abdominal aortic aneurysm repair systemwith drugs, agents and/or compounds which promote wound healing asdescribed below. For example, portions of the exemplary system 1000,illustrated in FIG. 27, may be coated with one or more drugs, agentsand/or compounds that induce or promote the wound healing process,thereby reducing or substantially reducing the risk of endoleaks. It maybe particularly advantageous to coat the ends of the two secondprostheses 1004 and 1006 and the entire first prosthesis 1002, as theseare the most likely regions for endoleaks. However, coating the entirestent-graft, i.e. graft material and stent, may prove beneficialdepending upon the type of endoleak. Since it is not always possible tostop endoleaks utilizing currently available methods, the use of woundhealing agents, delivered locally, in accordance with the presentinvention may serve to effectively stop or prevent acute and chronicendoleaks. It is important to note that the present invention may beutilized in combination with any abdominal aortic aneurysm repairsystem, or with any other type of graft component where leakage is apotential problem. The present invention may be utilized in conjunctionwith type I, III, IV and V endoleaks.

[0220] Normal wound healing essentially occurs in three stages orphases, which have a certain degree of overlap. The first phase iscellular migration and inflammation. This phase lasts for several days.The second phase is the proliferation of fibroblasts for two to fourweeks with new collagen synthesis. The third phase is remodeling of thescar and typically lasts from one month to a year. This third phaseincludes collagen cross linking and active collagen turnover.

[0221] As stated above, there are certain drugs, agents and/or compoundsthat may be delivered locally to the repair site, via the repair system,that promotes wound healing which in turn may eliminate or substantiallyreduce the incidence of endoleaks. For example, increased collagenproduction early in wound healing leads to greater wound strength.Accordingly, collagen may be combined with the repair system to increasewound strength and promote platelet aggregation and fibrin formation. Inaddition, certain growth factors may be combined with the repair systemto promote platelet aggregation and fibrin formation as well as toincrease wound strength.

[0222] Platelet-derived Growth Factor induces mitoses and is the majormitogen in serum for growth in connective tissue. Platelet Factor 4 is aplatelet released protein that promotes blood clotting by neutralizingheparin. Platelet-derived Growth Factor and Platelet Factor 4 areimportant in inflammation and repair. They are active for humanmonocytes, neutrophils, smooth muscle cells, fibroblasts andinflammation cells. Transforming Growth Factor-β is a part of a complexfamily of polypeptide hormones or biological factors that are producedby the body to control growth, division and maturation of blood cells bythe bone marrow. Transforming Growth Factor-β is found in tissues andplatelets, and is known to stimulate total protein, collagen and DNAcontent in wound chambers implanted in vivo. Transforming GrowthFactor-β in combination with collagen has been shown to be extremelyeffective in wound healing.

[0223] A series of reactions take place in the body whenever a bloodclot begins to form. A major initiator of these reactions is an enzymesystem called the Tissue Factor/VIIa complex. Accordingly, TissueFactor/VIIa may be utilized to promote blood clot formation and thusenhance wound healing. Other agents which are known to initiate thrombusformation include thrombin, fibrin, plasminogin-activator initiator,adenosine diphosphate and collagen.

[0224] The use of these drugs, agents and/or compounds in conjunctionwith the various components of the repair system may be used toeliminate or substantially reduce the incidence of endoleaks through theformation of blood clots and wound healing.

[0225] The stent and/or graft material comprising the components of thesystem 1000 may be coated with any of the above-described drugs, agentsand/or compounds. The above-described drugs, agents and/or compounds maybe affixed to a portion of the components or to all of the componentsutilizing any of the materials and processes described above. Forexample, the drugs, agents and/or compounds may be incorporated into apolymeric matrix or affixed directly to various portions of thecomponents of the system.

[0226] The particular polymer(s) utilized depends on the particularmaterial upon which it is affixed. In addition, the particular drug,agent and/or compound may also affect the selection of polymer(s).

[0227] Although shown and described is what is believed to be the mostpractical and preferred embodiments, it is apparent that departures fromspecific designs and methods described and shown will suggest themselvesto those skilled in the art and may be used without departing from thespirit and scope of the invention. The present invention is notrestricted to the particular constructions described and illustrated,but should be constructed to cohere with all modifications that may fallwithin the scope of the appended claims.

What is claimed is:
 1. A system for bypassing an aneurysm comprising: atleast one prosthesis for establishing a fluid flow path through ananeurysmal section of artery; an anchoring element operativelyassociated with the at least one prosthesis for securing and sealing theat least one prosthesis upstream of the aneurysmal section of artery; abiocompatible vehicle affixed to at least one of the anchoring elementand the at least one prosthesis; and at least one agent in therapeuticdosages incorporated into the biocompatible material for the promotionof a wound healing response.
 2. The system for bypassing an aneurysmaccording to claim 1, wherein the at least one prosthesis comprises astent-graft.
 3. The system for bypassing an aneurysm according to claim2, wherein the stent-graft comprises a stent and a graft materialsecured to at least a portion of the stent.
 4. The system for bypassingan aneurysm according to claim 3, wherein the stent is self-expanding.5. The system for bypassing an aneurysm according to claim 4, whereinthe graft material comprises a polymeric material.
 6. The system forbypassing an aneurysm according to claim 5, wherein the anchoringelement comprises a scaffold structure at least partially covered with agasket material substantially impervious to blood.
 7. The system forbypassing an aneurysm according to claim 6, wherein the biocompatiblevehicle comprises a polymeric matrix.
 8. The system for bypassing ananeurysm according to claim 7, wherein the biocompatible vehiclecomprises a polyfluoro copolymer comprising polymerized residue of afirst moiety selected from the group consisting of vinylidenefluorideand tetrafluoroethylene, and polymerized residue of a second moietyother than the first moiety and which is copolymerized with the firstmoiety, thereby producing the polyfluoro copolymer, wherein the relativeamounts of the polymerized residue of the first moiety and thepolymerized residue of the second moiety are effective to produce thebiocompatible vehicle with properties effective for use in coatingimplantable medical devices when the coated medical device is subjectedto a predetermined maximum temperature, and a solvent in which thepolyfluoro copolymer is substantially soluble.
 9. The system forbypassing an aneurysm according to claim 8, wherein the polyfluorocopolymer comprises from about fifty to about ninety-two weight percentof the polymerized residue of the first moiety copolymerized with fromabout fifty to about eight weight percent of the polymerized residue ofthe second moiety.
 10. The system for bypassing an aneurysm according toclaim 8, wherein said polyfluoro copolymer comprises from about fifty toabout eighty-five weight percent of the polymerized residue ofvinylidenefluoride copolymerized with from about fifty to about fifteenweight percent of the polymerized residue of the second moiety.
 11. Thesystem for bypassing an aneurysm according to claim 8, wherein saidcopolymer comprises from about fifty-five to about sixty-five weightpercent of the polymerized residue of the vinylidenefluoridecopolymerized with from about forty-five to about thirty-five weightpercent of the polymerized residue of the second moiety.
 12. The systemfor bypassing an aneurysm according to claim 8, wherein the secondmoiety is selected from the group consisting of hexafluoropropylene,tetrafluoroethylene, vinylidenefluoride, 1-hydropentafluoropropylene,perfluoro (methyl vinyl ether), chlorotrifluoroethylene,pentafluoropropene, trifluoroethylene, hexafluoroacetone andhexafluoroisobutylene.
 13. The system for bypassing an aneurysmaccording to claim 8, wherein the second moiety is hexafluoropropylene.14. The system for bypassing an aneurysm according to claim 1, whereinthe at least one agent comprises a growth factor.
 15. The system forbypassing an aneurysm according to claim 14, wherein the growth factorcomprises Platelet-derived Growth Factor.
 16. The system for bypassingan aneurysm according to claim 14, wherein the growth factor comprisesTransforming Growth Factor-β.
 17. The system for bypassing an aneurysmaccording to claim 1, wherein the at least one agent comprisesTransforming Growth Factor-β and collagen.
 18. The system for bypassingan aneurysm according to claim 1, wherein the at least one agentcomprises Tissue Factor/VIIa.
 19. The system for bypassing an aneurysmaccording to claim 1, wherein the at least one agent comprises collagen.20. The system for bypassing an aneurysm according to claim 1, whereinthe at least one agent comprises thrombus formation compounds.
 21. Asystem for bypassing an aneurysm comprising: at least one prosthesis forestablishing a fluid flow path through an aneurysmal section of artery;an anchoring element operatively associated with the at least oneprosthesis for securing and sealing the at least one prosthesis upstreamof the aneurysmal section of artery; and at least one agent intherapeutic dosages affixed to at least one of the anchoring element andthe at least one prosthesis for the promotion of a wound healingresponse.
 22. The system for bypassing an aneurysm according to claim21, wherein the at least one prosthesis comprises a stent-graft.
 23. Thesystem for bypassing an aneurysm according to claim 22, wherein thestent-graft comprises a stent and a graft material secured to at least aportion of the stent.
 24. The system for bypassing an aneurysm accordingto claim 23, wherein the stent is self-expanding.
 25. The system forbypassing an aneurysm according to claim 24, wherein the graft materialcomprises a polymeric material.
 26. The system for bypassing an aneurysmaccording to claim 25, wherein the anchoring element comprises ascaffold structure at least partially covered with a gasket materialsubstantially impervious to blood.
 27. The system for bypassing ananeurysm according to claim 21, wherein the at least one agent comprisesa growth factor.
 28. The system for bypassing an aneurysm according toclaim 27, wherein the growth factor comprises Platelet-derived GrowthFactor.
 29. The system for bypassing an aneurysm according to claim 27,wherein the growth factor comprises Transforming Growth Factor-β. 30.The system for bypassing an aneurysm according to claim 21, wherein theat least one agent comprises Transforming Growth Factor-p and collagen.31. The system for bypassing an aneurysm according to claim 21, whereinthe at least one agent comprises Tissue Factor/VIIa.
 32. The system forbypassing an aneurysm according to claim 21, wherein the at least oneagent comprises collagen.
 33. The system for bypassing an aneurysmaccording to claim 21, wherein the at least one agent comprises thrombusformation compounds.
 34. The system for bypassing an aneurysm accordingto claim 33, wherein the thrombus formation compound comprises thrombin.35. The system for bypassing an aneurysm according to claim 33, whereinthe thrombus formation compound comprises fibrin.
 36. The system forbypassing an aneurysm according to claim 33, wherein the thrombusformation compound comprises plasminogin-activator initiator.
 37. Thesystem for bypassing an aneurysm according to claim 33, wherein thethrombus formation compound comprises adenosine diphosphate.